ABSTRACT REYNOLDS, WILLIAM CASEY. The Impacts of Athletic Field Paint on Light Spectral

ABSTRACT

REYNOLDS, WILLIAM CASEY. The Impacts of Athletic Field Paint on Light Spectral

Quality, Turfgrass Photosynthesis, and Transpiration in Painted Turfgrass Canopies. (Under

the direction of Dr. Grady Miller.)

Athletic field paints are applied to turf surfaces with little or no acute injury.

However, field managers often notice chronic declines in turfgrass health after repeated

applications. This study examines the impacts of athletic field paint on light spectral quality,

photosynthesis, and transpiration in painted turfgrass canopies. Athletic field paints produce

various colors through selective reflection, transmission, and absorption of visible light (400-

700 nm). However, photosynthetically active radiation (PAR) also exists at these

wavelengths, and as a result it was hypothesized that alterations in visible light to produce

specific colors would lead to reductions in photosynthetically active radiation (PAR) and

total canopy photosynthesis (TCP). Athletic field paints may also impact transpiration by

obstructing gas exchange at the leaf surface, which could potentially lead to reductions in

TCP and transpiration as well as increases in canopy temperature above optimal ranges.

Lab experiments using a spectroradiometer and integrating sphere examined the

impacts of athletic field paint color and dilution on reflection, transmission, and absorption of

PAR as well as wavelengths within PAR. Subsequent growth chamber experiments were

used to examine how these impacts related to turfgrass photosynthesis and transpiration.

Photosynthesis was evaluated in ‘Palmer V’ perennial ryegrass (Lolium perenne L.) using a

gas exchange system 24 h after application of red and white athletic field paint at two

dilutions as well as in ‘Tifway’ bermudagrass [Cynodon dactylon (L.) Pers. x C.

transvaalensis Burtt-Davy] 24 h after application of ten colors. Transpiration of Tifway as a

result of six paint colors was evaluated using mass balance methods. Canopy temperature

was measured in all experiments using an infrared digital thermometer immediately prior to

measurements of photosynthesis and transpiration.

Spectroradiometry analyses revealed the significant effects of paint color (P ≤ 0.001)

and dilution (P ≤ 0.0001) on reflection, transmission, and absorption of PAR. Lighter colors

including white, yellow, orange and red reflected 47-92% of PAR, while darker colors

including green, black, and dark blue absorbed 87- 95% of PAR. Accompanying gas

exchange measurements revealed that all treatments reduced TCP based upon color (P ≤

0.0001) and dilution (P ≤ 0.0001). Values for TCP were most negatively correlated with

absorption of PAR (r = -0.959; P ≤ 0.001) and was positively correlated with reflection and

transmission of PAR. Transpiration in Tifway canopies was reduced by paint application (P ≤

0.0001) where lighter colors yellow and white reduced transpiration the least while black

and blue reduced transpiration the most. Canopy temperature was affected by paint color (P ≤

0.0001) in all growth chamber experiments and was most positively correlated with PAR

absorption (r = 0.872; P ≤ 0.001) over the range of the ten colors examined. Black and blue

resulted in the largest increases in canopy temperature (39.6 and 40.5oC), which is above the

optimal range of 27-35oC, potentially resulting in heat stress.

The results presented in these experiments reveal the color-dependent relationship

between available PAR, TCP, and transpiration in painted turfgrass canopies. The overlap of

visible light and PAR results in secondary impacts on turfgrass growth including shading,

stomatal obstruction, and heat stress. These factors clearly indicate that damage to turfgrasses

with long-term painting will be difficult to avoid, and this is particularly true with darker

colors of paint.

The Impacts of Athletic Field Paint on Light Spectral Quality, Turfgrass Photosynthesis,

and Transpiration in Painted Turfgrass Canopies

by

William Casey Reynolds

A dissertation submitted to the Graduate Faculty of

North Carolina State University

in partial fulfillment of the

requirements for the degree of

Doctor of Philosophy

Crop Science

Raleigh, North Carolina

2013

APPROVED BY:

_______________________________ ______________________________

Dr. Grady L. Miller Dr. Thomas W. Rufty

Co-Chair of Advisory Committee Co-Chair of Advisory Committee

_______________________________ ______________________________

Dr. Randy Wells Dr. David P. Livingston III

_______________________________

Dr. Michael Paesler

ii

BIOGRAPHY

William Casey Reynolds was born on 28 September 1978 to Bill and Vivian

Reynolds and has an older brother, Clifton Reynolds, who was born two years prior on 28

April 1976. He grew up in Midland, NC and graduated from Central Cabarrus High School

in 1996. Upon graduation he moved to Raleigh, NC in pursuit of an education in the College

of Agriculture and Life Sciences at North Carolina State University. After his sophomore

year, he decided to focus on a Bachelor of Science Degree in Crop Science with a

concentration in turfgrass management, which he received in May 2000.

Over the course of his undergraduate career, Mr. Reynolds spent his summers

working in the landscape industry, the golf course industry, and athletic field construction.

These combined experiences proved invaluable and were an integral part of his decision to

further pursue his education by entering graduate school at NC State in the fall of 2000 in

which he pursued a Master of Science degree in Crop Science with a concentration in

Turfgrass Management and minor in Business Management.

In 2003, upon completion of his Master of Science degree from NC State, Mr.

Reynolds’ path diverged in two directions. He was offered a position at NC State as Dr. Art

Bruneau’s turfgrass research and extension associate while at the same time became

owner/operator of a landscaping business he named Graduate Degree Turf. Over the course

of the next five years, Mr. Reynolds worked both of these positions before deciding to re-

enter graduate school at NC State in pursuit of a Doctor of Philosophy in Crop Science.

As of 2013, he is nearing the completion of this degree and currently resides in

Raleigh, NC where he lives with his fiancée Diane Silcox, whom he will be married to on

iii

October 19th

, 2013, his golden retriever Ella, and the world’s spottiest beagle, Mandy. Upon

completion of his PhD, Mr. Reynolds is looking forward to continuing his career in the

turfgrass industry.

iv

ACKNOWLEDGMENTS

I wish to express my sincere gratitude to my graduate committee including Dr. Grady

Miller, Dr. Tom Rufty, Dr. Randy Wells, Dr. David Livingston, and Dr. Michael Paesler. I

have enjoyed working with each of them on this project and am very proud of the work we

have completed into the investigation of athletic field paint on turfgrass health. I am also very

thankful to Dr. Susana Milla-Lewis, who has been not only been very supportive of my

education, but has also been a great inspiration and role model to me as a faculty member

early in her career with the ambition to seek tenure at such a respectable institution as NC

State. I have learned an immense amount from each of these professors regarding how to

conduct ethical and meaningful research that has the potential to impact the turfgrass industry

in North Carolina and beyond. On a personal level, I consider each of them as friends and

colleagues much more so than graduate committee members and supervisors. I highly respect

each of these faculty members for both their academic and personal integrity, and I greatly

appreciate the time they have devoted to my education. Any professional success I have in

my career is a direct result of their hard work and dedication to the completion of my PhD.

I would also like to acknowledge Dr. Bob Patterson for his encouragement and

support throughout my career and education at NC State. Thanks also to Scott Brinton and

George Sajner with Pioneer Athletics, who each helped tremendously with this work and

without which, it would not have been a success. Finally, thanks to all of my other friends

and colleagues at NC State and beyond who made this period in my life one that I will

always look back on with great pride and enjoyment.

v

TABLE OF CONTENTS

LIST OF TABLES ....................................................................................................... vi

LIST OF FIGURES .................................................................................................... ix

LITERATURE REVIEW ..............................................................................................1

ATHLETIC FIELD PAINT IMPACTS LIGHT SPECTRAL QUALITY .....................

AND TURFGRASS PHOTOSYNTHESIS .................................................................24

Abstract .............................................................................................................25

Introduction .......................................................................................................26

Materials and Methods ......................................................................................28

Results ...............................................................................................................32

Discussion .........................................................................................................36

References .........................................................................................................44

ATHLETIC FIELD PAINT COLOR DIFFRENTIALLY ALTERS LIGHT

SPECTRAL QUALITY AND BERMUDAGRASS PHOTOSYNTHESIS ...............56

Abstract .............................................................................................................57

Introduction .......................................................................................................58


Results ...............................................................................................................64

Discussion .........................................................................................................68

References .........................................................................................................74

ATHLETIC FIELD PAINT COLOR IMPACTS TRANSPIRATION AND

CANOPY TEMPERATURE IN BERMUDAGRASS ...............................................84

Abstract .............................................................................................................85

Introduction .......................................................................................................86


Results ...............................................................................................................92

Discussion .........................................................................................................96

References .......................................................................................................103

vi

LIST OF TABLES

ATHLETIC FIELD PAINT IMPACTS LIGHT SPECTRAL QUALITY

AND TURFGRASS PHOTOSYNTHESIS

Table 1. Reflection, transmission, and absorption of photosynthetically

active radiation (400-700nm) by red and white paint averaged

over six wet thicknesses (0.125, 0.250, 0.375, 0.500, 0.625, and

0.750 mm) using an integrating sphere and spectroradiometer ............46

Table 2. Intercepts, linear, quadratic, cubic coefficients and standard error

for regression equations of reflection, transmission, and absorption

of photosynthetically active radiation (PAR) (400-700nm) by red

and white paint at six wet thicknesses (0.125, 0.25, 0.375, 0.5,

0.625, and 0.75 mm) using an integrating sphere and

spectroradiometer .................................................................................47

Table 3. Reflection, transmission, and absorption of light at narrow-band

and broad-band wavelengths by red no dilution, red 1:1 dilution,

white no dilution, and white 1:1 dilution paint when applied to

transparency film at 0.050mm dried thickness ....................................48

Table 4. Analysis of variance for perennial ryegrass photosynthetic response

from weekly applications of red and white paint (no dilution and 1:1

dilution) treatments and unpainted control in a controlled

environment growth chamber during two 6-wk experiments at the

Southeastern Plant Environment Laboratory in Raleigh, NC ..............49

Table 5. Perennial ryegrass total canopy photosynthesis (TCP) and

temperature responses from various paint applications treatments

during two 6-wk experiments at the Southeastern Plant

Environment Laboratory in Raleigh, NC .............................................50

Table 6. Analysis of variance for perennial ryegrass photosynthetic response

due to zero, one, two, three, or four weekly treatments of red non-

diluted paint during two 6-wk experiments in a controlled

environment growth chamber at the Southeastern Plant

Environment Laboratory in Raleigh, NC .............................................51

Table 7. Perennial ryegrass total canopy photosynthesis (TCP) and

temperature responses from 0, 1, 2, 3, or 4 applications of red no

dilution paint during two 6-wk experiments at the Southeastern

Plant Environment Laboratory in Raleigh, NC....................................52

vii


SPECTRAL QUALITY AND BERMUDAGRASS PHOTOSYNTHESIS

Table 1. Pantone Matching System (PMS) numbers for ten colors of

athletic field turf paint. .........................................................................77

Table 2. Reflection, transmission, and absorption of light in the 400 to 500

nm, 600 to 700 nm, and 400 to 700 nm wavelength ranges by ten

colors of athletic field paint .................................................................78

Table 3. Analysis of variance for normalized total canopy photosynthesis

(TCP) from weekly applications of ten colors of athletic field paint

in a controlled environment growth chamber during two 5-wk

experiments at the Southeastern Plant Environment Laboratory in

Raleigh, NC..........................................................................................79

Table 4. Pearson’s correlation coefficients for reflection, transmission, and

absorption of light through black, dark blue, green, light blue,

maroon, orange, purple, red, white, and yellow paint when

correlated to total canopy photosynthesis (TCP) and canopy

temperature during two 5-wk experiments ..........................................80


CANOPY TEMPERATURE IN BERMUDAGRASS

Table 1. Pantone Matching System (PMS) numbers for six colors of

athletic field turf paint ........................................................................106

Table 2. Daily water loss (mm day-1

) and canopy temperature in ‘Tifway’

bermudagrass as a result of six day/night air temperature

treatments (26/22, 29/22, 32/22, 35/22, and 38/22oC) in a

controlled environment growth chamber during two 5-wk

experiments at the Southeastern Plant Environment Laboratory

in Raleigh, NC ...................................................................................107

Table 3. Analysis of variance for ‘Tifway’ bermudagrass daily water loss

(mm day-1

) as a result of six day/night air temperature treatments

(26/22, 29/22, 32/22, 35/22, and 38/22oC) in a controlled

environment growth chamber during two 5-wk experiments at the

Southeastern Plant Environment Laboratory in Raleigh, NC ............108

viii

Table 4. Analysis of variance for ‘Tifway’ bermudagrass daily water loss

(mm day-1

) due to weekly applications of six colors of athletic field

paint in a controlled environment growth chamber during two

experiments at the Southeastern Plant Environment Laboratory in

Raleigh, NC........................................................................................109

Table 5. Daily water loss and temperature response in ‘Tifway’

bermudagrass from weekly applications of six colors of athletic

field paint during two 5-wk experiments at the Southeastern Plant

Environment Laboratory in Raleigh, NC ...........................................110

Table 6. Quadratic discriminant analysis of canopy temperature (oC) and

daily water loss (mm day-1

) in ‘Tifway’ bermudagrass as a result

of weekly applications of six colors of athletic field paint and an

un-painted control during two 5-wk experiments at the

Southeastern Plant Environment Laboratory in Raleigh, NC ............111

ix

LIST OF FIGURES

ATHLETIC FIELD PAINT IMPACTS LIGHT SPECTRAL QUALITY

AND TURFGRASS PHOTOSYNTHESIS

Figure 1. Reflection (a), transmission (b), and absorption (c) of

photosynthetically active radiation (400-700nm) of red non-

diluted, red 1:1 diluted, white non-diluted, and white 1:1 diluted

paint when applied to transparent film at six wet thicknesses (0.125,

0.250, 0.375, 0.500, 0.625, and 0.750 mm). Each data point is the

mean of three replicates. Scales for each y-axis are based on

minimum and maximum percent photosynthetically active radiation

for each observation .............................................................................53

Figure 2. Normalized photosynthetic rates of perennial ryegrass measured

24 h after zero, one, two, three, or four successive weekly

applications of red non-diluted paint in a controlled environment

growth chamber at the Southeastern Plant Environment Laboratory

in Raleigh, NC. Data points at weeks five and six were collected 1

and 2 wk, respectively, after the last paint application ........................54

Figure 3. Dried thickness of paint treatments applied at 0.125, 0.250, 0.375,

0.500, 0.625, and 0.750 mm wet thickness ..........................................55


SPECTRAL QUALITY AND BERMUDAGRASS PHOTOSYNTHESIS

Figure 1. Illustration of reflection, transmission, and absorption of light by

athletic field paint applied to a turfgrass leaf .......................................81

Figure 2. Normalized total canopy photosynthesis (TCP) rates of ‘Tifway’

bermudagrass 24 h after application of ten colors of athletic field

paint during two 5-wk experiments in a controlled environment

growth chamber at the Southeastern Plant Environment Laboratory

in Raleigh, NC. Values for TCP were averaged over five weeks

and are reported as percent of un-painted control. Bars above each

treatment represent standard error .......................................................82

x

Figure 3. Correlations of reflection, transmission, and absorption of PAR

(400-700 nm) with normalized total canopy photosynthesis (TCP)

rates of ‘Tifway’ bermudagrass 24 h after application of ten colors

of athletic field paint during two 5-wk experiments in a controlled

environment growth chamber at the Southeastern Plant Environment

Laboratory in Raleigh, NC. Values for TCP were averaged over five

weeks and are reported as percent of un-painted control ....................83


CANOPY TEMPERATURE IN BERMUDAGRASS

Figure 1. Average daily water loss (mm day-1

) of ‘Tifway’ bermudagrass

measured every 24 h for six days during two 5-wk experiments in

a controlled environment growth chamber at the Southeastern Plant

Environment Laboratory in Raleigh, NC. Values represent daily

average water loss, and bars for each treatment represent standard

error ....................................................................................................112

Figure 2. Daily water loss (mm day-1

) and canopy temperature (oC) of

‘Tifway’ bermudagrass measured every 24 h for six days per week

during two 5-wk experiments in a controlled environment growth

chamber at the Southeastern Plant Environment Laboratory in

Raleigh, NC........................................................................................113

Figure 3. Digital images of 20µm cross-sections of ‘Tifway’ bermudagrass

after one application of white and black athletic field paint. White

paint has been diluted with water at v:v ratio of 1:1 and black paint

was not diluted. Images were taken at 10x magnification and

cropped to an image size of 856 x 560 pixels ....................................114

1

LITERATURE REVIEW

Athletic field paints are routinely applied to field surfaces for marking regulation

lines, logos, advertisements, etc. in sporting events worldwide. These products are

formulated with the intent that they do not cause any acute injury when properly applied, yet

it is widely recognized that repeated paint applications often degrade turfgrass quality.

Although the cause(s) of the damage is unknown, a potential explanation lies in secondary,

chronic effects on plant growth processes. Two processes that are likely affected by athletic

field paint applications are photosynthesis and transpiration. Photosynthesis is the most

fundamental and important chemical reaction in plants and literally means “synthesis using

light” (Taiz and Zeiger, 2010). Photosynthesis is a biological process unique to plants that

allows them to use solar radiation to reduce atmospheric carbon dioxide (CO2) into usable

forms of energy. Atmospheric CO2 enters the leaf in a process called transpiration, while

photosynthesis produces the energy used to reduce it by oxidizing water (H2O). These two

processes are fundamental to the survival and performance of all plants, including

turfgrasses, and it is reasonable to suspect that athletic field paint applications could have

substantial impacts on each.

Photosynthesis

Photosynthesis was first discovered by Joseph Priestley in 1771 who discovered that a

sprig of mint growing in the air in which a candle had burned out improved the air so another

candle could burn (Bronkowski, 1973). This was used not only to explain fire, but also that

oxygen was one component of the air that we breathe and that it is expelled by plants. Later

2

experiments established the essential role of light, CO2, and H2O as inputs in photosynthesis

and that O2 and carbohydrates were by-products. The balanced overall chemical reaction for

photosynthesis is often written as follows:

6 CO2 + 6 H2O C6H12O6 + 6O2 Carbon Water Carbohydrate Oxygen

Dioxide

Photosynthesis most often occurs in leaf mesophyll cells which contain light absorbing

pigments called chlorophylls. Specifically, chlorophyll pigments are found within leaf

mesophyll cells in subcellular organelles called chloroplasts. These chloroplasts are the site

of the light reactions of photosynthesis.

The light reactions are of importance in athletic field paint research due to the

potential impacts of paint on the availability of light to drive these reactions. All solar energy

(light) has properties of waves, measured in wavelengths (λ), as well as particles, called

photons. These photons deliver energy that is dependent on the frequency (ν) at which waves

pass a given place in a given time. However, only the wavelengths between 400 and 700 nm

are capable of delivering energy that is usable in the light reactions of photosynthesis. As

such, light within these wavelengths is commonly referred to as photosynthetically active

radiation (PAR). It is also important to note that within PAR, there are particular spectral

bands that are most effectively absorbed for photosynthesis. These bands include

wavelengths between 400-500 nm and 600-700 nm (Taiz and Zeiger, 2010). Light between

500-600 nm is not effectively absorbed for photosynthesis due to the properties of

chlorophyll pigments that preferentially reflect light within this wavelength range. Within

the 400-500 nm and 600-700 nm ranges, Chlorophyll a is known to have peak spectral

3

absorption at 410, 430, and 660 nm while peak absorption for Chlorophyll b occurs at 430

and 640 nm (Taiz and Zeiger, 2010).

In order to maximize absorption of PAR, and thus maximize photosynthetic rates,

mesophyll cells containing chloroplasts are often located immediately below the upper

epidermis of the leaf where they are most likely to receive incident radiation. As a result,

athletic field paint applications that are applied to coat leaf surfaces may be capable of

reducing incident PAR, thus reducing the amount of energy readily available to drive the

light reactions of photosynthesis. This is particularly true given the fact that like PAR, visible

light also exists between 400 and 700 nm. Visible light can be categorized by color and is a

direct result of wavelength. Red, orange, yellow, green, blue, indigo, and violet are often the

colors assigned to the visible spectrum and begin with violet as having the shortest

wavelengths (~ 400nm) and red having the longest (~ 700nm). The overlapping wavelength

range of PAR and visible light means that the ability of pigments to produce specific colors

by altering visible light are also likely to alter PAR, as well as wavelengths within PAR,

available for photosynthesis.

The impacts of reduced light quantity and altered light quality on turfgrass growth

have been examined in studies of shading from trees, buildings, and weeds (Bell et al., 2000;

Gaskin, 1965; McKee, 1963). Reductions and alterations in light have also been linked to

reductions in turf performance as well as physiological changes within grasses (McBee,

1969; Dudeck and Peacock, 1992; Wilkinson and Beard, 1975). Athletic field paint has yet to

be linked to PAR reductions, but several studies have linked PAR reductions as a result of

varying types of shade with reduced turfgrass performance. For example, decreased turfgrass

4

growth as a result of reductions in PAR has been reported by Baldwin et al. (2009) where it

was found that shade fabrics filtering wavelengths 360 to 720 nm produced clipping yields in

‘Tifway’ bermudagrass [Cynodon dactylon (L.) Pers. X C. transvaalensis Burtt-Davy] of

only 21.4% of treatments receiving no shade. These shade fabrics reduced PAR by 65% from

an initial light intensity of 1,974 µmol m-2

s-1

to 895 µmol m-2

s-1

, which led to unacceptable

turfgrass quality of Tifway.

Other research has linked overall reductions in PAR to light compensation points, the

point at which CO2 photosynthetic fixation equals CO2 respiratory release. Edenfield (2001)

reported light compensation points of Floradwarf and Tifdwarf to range between 265 and 429

µmol m-2

s-1

in various shade treatments. As such, reductions in PAR that would result in

CO2 fixation below these levels would likely result in plant health decline.

In regard to specific wavelengths within PAR, Baldwin et al. (2009) found that shade

fabrics that selectively filtered wavelengths of light within PAR reduced growth. For

example, shade fabrics filtering wavelengths 560 to 720 nm, yet allowing passage of blue

light (400 to 500 nm) for 6 wk, resulted in a 38% reduction in clipping yields of Tifway.

Shade cloths filtering 360 to 520 nm and 360 to 560 nm while allowing passage of red light

(600 to 700 nm) also reduced clipping yields.

In addition to amount and type of shade, the duration under which turfgrasses are

subjected to shade is also important. In the Baldwin et al. (2009) study, turfgrass quality and

clipping yield of bermudagrass and zoysiagrass (Zoysia matrella (L.) Merr.) decreased as

duration of shade increased. Reductions in traffic tolerance were also observed in several

bermudagrass and zoysiagrass cultivars as the duration under shade and number of traffic

5

applications increased (Trappe et al., 2011). The notion that reductions in turfgrass quality

and performance are caused by chronic shading by athletic field paint applications is

consistent with athletic field paints not being acutely toxic to turfgrasses. Also, anecdotal

evidence from professional athletic field managers indicates that decreased growth and

density from athletic field paint applications are usually noticed only after multiple painting

events. These decreases become more severe as the number of paint applications increase.

In addition to absorption of PAR by paint pigments that may result in shading effects,

it is also worth investigating the reflection and transmission of PAR within painted turfgrass

canopies. This is due to the fact that reflection, transmission, and absorption are all inter-

related. For example, pigments found in red athletic field paint selectively reflect red

wavelengths while transmitting and absorbing all other wavelengths. Pigments found in

white paint reflect light at all wavelengths, while pigments found in black paint absorb all

wavelengths.

Previous research performed in other crops has shown that available PAR can be

altered by reflection of visible light from various colors of paint and is sufficient to affect

plant growth. Kasperbauer (2000) found that upwardly reflected light from painted plastic

covers beneath cotton (Gossypium hirsutum L.) canopies differed by color. Plants grown over

plastic surfaces painted white received substantially more PAR than plants grown over

plastics painted red and green. In a separate study, it was found that carrots (Daucus carota

L.) grown over plastic mulches painted white, yellow, red, blue, and green received varying

amounts of reflected PAR (Antonious and Kasperbauer, 2002). Up to this time, however, no

such studies have been conducted with paint applied to turfgrass.

6

Transpiration

As previously discussed, the impacts of various colors of athletic field paint on

reflection, transmission, and absorption of PAR are only one component of photosynthesis.

In addition to PAR driving the light reactions, transpiration provides the necessary

atmospheric CO2 to facilitate the dark reactions, which also has the potential to be impacted

by paint. Stomata serve as the entry point of atmospheric CO2 into the plant as well the exit

point for H2O vapor and oxygen. Stomata are enclosed on either side by guard cells which

are specialized cells in the epidermis that are morphologically distinct from general

epidermal cells (Franks and Farqhuar, 2007). Location and frequency of stomata are species

dependent, but they have been documented to occur only on the lower (abaxial) leaf surface,

only on the above (adaxial) leaf surface), and on both surfaces. However, in most plant

species, stomata can be found on both surfaces with the majority on the abaxial surface

(Ticha, 1982). Within grasses commonly used as turf, stomata can vary by species and

carbon fixation pathway but are commonly found on both the abaxial and adaxial surfaces

(Green et al., 1993).

Stomata are some of the most important features of plants within all species because

of their integral role in gas exchange and temperature regulation. The delicate balance of

opening and closing stomata is regulated by many environmental factors including

atmospheric CO2 concentration, temperature, humidity, soil/plant moisture status, etc.

However, one of the most important external factors regulating stomatal opening and closing

is the availability of light, specifically in the blue (400-500nm) and red (600-700nm)

7

wavelengths. These are deemed the “blue-light” response, which is independent of

photosynthesis (PS) and the “red-light” response, which is tied closely to photosynthesis.

The blue-light response occurs only in guard cells while the red-light response occurs

in both guard cells and mesophyll cells (Shimazaki, 2007). In guard cells, blue light activates

a plasma membrane H+-ATPase that pumps protons out of the guard cells resulting in a

lowered pH in the apoplastic space surrounding the guard cells. This lower pH generates a

gradient that allows ions to flow into guard cells resulting in increased turgor and stomatal

opening.

The signaling response of blue light via the H+-ATPase is countered by a somewhat

disputed signaling response of red light. The red-light response has traditionally been thought

of as a photosynthesis driven response where stomata respond to a decrease in the internal

carbon dioxide concentration (Ci) due to active photosynthesis under saturating red light

capable of driving photosynthesis.

Regardless of the individual blue and red light responses there is little doubt that there

is a synergistic response resulting from illumination with both blue and red wavelengths of

light. Red-light driven photosynthesis in mesophyll and guard cell chloroplast result in

increased stomatal aperture while blue-light signaling has the capacity to open stomata even

further. If athletic field paint applications are capable of reducing PAR, as well as

wavelengths within PAR, it is also reasonable to suspect that decreases in blue and red light

reaching the leaf as result of paint application and color may impact stomatal opening.

Another means by which transpiration may be negatively affected by athletic field

paint is through the physical obstruction of stomata. If athletic field paints are capable of

8

clogging stomata then the rate at which CO2 enters into the leaf could be slowed or even

prevented all together. As such, decreased CO2 entry into the leaf would most certainly have

negative impacts on turfgrass health and performance. As is the case with the effects of

athletic field pain on photosynthesis, the effects of athletic field paint on transpiration is an

area of research that has yet to be conducted.

Heat Stress

In addition to providing CO2 as a substrate for the carbon fixation reactions,

transpiration’s ability to exchange CO2 for O2 and H2O vapor has a secondary benefit to

plants. Transpiration allows plants to lower their internal temperature by converting internal

liquid H2O to H20 vapor. As this phase conversion occurs, the temperature of the H2O itself

does not change, but the surface from which the H2O evaporates is lowered. This process

helps to moderate the temperature of transpiring leaves which may otherwise increase

substantially with absorption of solar radiation. The temperature optimum for turfgrasses is

generally considered to range from 16-24 oC in cool-season turf and 27-35

oC in warm-

season turf while supra-optimal temperatures are often considered to be 10oC above optimal

(Dipaola and Beard, 1992; Huang et al., 2009). Negative impacts of increasing temperature

above these optimal ranges include excessive H2O loss, increased C losses from

photorespiration, lower rates of photosynthesis, and decreased activation of the ribulose 1,5-

bisphosphate carboxylase-oxygenase (Rubisco) enzyme.

The impacts of increasing soil and air temperature on turfgrass health and

performance have been widely documented in un-painted turfgrasses, particularly with

9

regard to increased C losses from photorespiration and lower rates of photosynthesis. Huang

and Gao (2000); Huang and Xu (2000); Huang et al., 2008 found that creeping bentgrass

whole plant and root respiration both increased as soil and air temperatures increased, with

soil temperatures having greater impacts. Furthermore, as the duration at elevated

temperatures increased, carbon consumption by respiration began to exceed carbon

production by photosynthesis resulting in many negative impacts on the plant including

reductions in turf quality, leaf chlorophyll content, root growth, photosynthesis, and total

non-structural carbohydrates. With regard to Rubisco, Crafts-Brander and Salvucci (2000)

reports decreases in Rubisco activation in cotton (Gossypium hirsutum) and tobacco

(Nicotiana rusticum) leaves when leaf temperatures exceeded 35oC. Furthermore, Salvucci

and Crafts-Brander (2004) reports that direct inhibitions on photosynthesis as a result of the

kinetic properties of Rubisco occur at temperatures higher than 30oC and defines moderate

heat stress as ranging from 30-42oC.

The impact of athletic field paint on temperature within the turfgrass canopy have

been an area of limited study, but there is certainly the potential for canopy temperatures to

increase as a result of paint application. This is due to the fact that many pigments, especially

those found in darker colors, are selected for their ability to absorb light (radiation). It is also

possible that if athletic field paint applications obstruct stomata then transpiration, and thus

evaporative cooling, may be reduced. Like photosynthesis and transpiration, the relationship

between athletic field paint applications and their effect(s) on turfgrass canopy temperature

has yet to be established.

10

Paint Chemistry

In order to fully understand the capacity for athletic field paint to affect PAR,

photosynthesis, transpiration, and canopy temperature it is important to explore the basic

fundamentals of paint chemistry and application. Manufacturers focus much of their efforts

on producing bright, distinct, uniform paints that are both affordable and non-injurious to

grass species commonly used on athletic field surfaces. Within the athletic field paint

industry, latex, water-based paints are the most commonly applied products. Athletic field

paints are no different than other paints in that they are formulated with enough opacity to

hide the painted substrate, in this case the turfgrass leaf, while at the same time producing the

perception of a desired color. Furthermore, all paints are composed of four main components:

resins (also called binders), pigments, solvents, and additives. Volatile components of paint

formulations include water, other solvents, and coalescing agents, each of which allows the

paint to remain in liquid suspension prior to application. However, these components are

designed to evaporate off of the leaf after application. Non-volatile components include

resins, pigments, extenders, and additives, and unlike volatile components they are each

designed to remain intact after application. These non-volatile components produce a paint

film consisting of pigments, extenders, and additives uniformly dispersed within the resin

that coats turfgrass tissues and remains intact after application. Therefore, any effects on

reflection, transmission, and absorption of visible light and PAR are a result of the non-

volatile components of the formulation. Furthermore, because pigments are selected for use

in various colors based almost solely on how they reflect, transmit, or absorb visible light it is

11

reasonable to conclude that pigments have the greatest potential to impact PAR and plant

growth processes.

The effects of paint color on specific wavelengths of light are a direct result of the

wide range of pigment sources used to produce various colors. Pigment sources for athletic

field paints include both inorganic and organic sources, each of which contribute various

properties with regard to color and application. Classification of all pigments into a

comprehensive system is difficult due to constantly evolving manufacturing methods, recent

improvements in paint properties, and new products. However, pigment classification in this

review will be defined using the traditional properties associated with inorganic and organic

pigments as defined by Lambourne and Strivens (1999).

Inorganic pigments possess excellent hiding power, extreme fastness to light and

weathering, and excellent color stability (Endrib, 1998). They also produce various optical

effects through non-selective or selective reflection and absorption of light. White, for

example, is produced by the non-selective scattering of visible light while black is a result of

the non-selective absorption of visible light. Various colors like red and yellow that are

derived from inorganic sources are produced by reflection and absorption of light that, unlike

white and black, is wavelength-dependent (Buxbaum and Pfaff, 2005). Regardless of

reflective and absorptive properties, many inorganic pigments like TiO2 (white), Fe2O3 red

(red) and C (black) are limited in the range of colors they can produce. Furthermore, most

inorganic pigments, with the exception of molybdate red, chrome yellow, and cadmium-

based pigments, lack tinting strength and therefore produce dull shades when added to white

to produce various colors (Herbst and Hunger, 2004). Other inorganic pigment sources such

12

as natural and synthetic Fe2O3 produce a wide variety of colors including yellow, orange, red,

and brown. Among natural and synthetic products, synthetic Fe2O3 pigments are more widely

used due to their pure hue, consistent properties, and tinting strength (Buxbaum and Pfaff,

2005).

Other pigment sources for orange and red include the organic pigments pyrazolone

orange and naphthol red, respectively. Pyrazolone orange is a low-cost, bright pigment with

good tinting strength, and as a result it is one of the most popular pigments for use in orange

paints (Lambourne and Strivens, 1999). It is also commonly added in small amounts to

yellow Fe2O3 to produce yellow. Napthol red is capable of producing a range of colors from

orange to mid-red, and like pyrazolone orange it is also widely used due to its low cost. Other

organic pigments like phthalocyanine green and blue, quinacridone magenta, and carbazole

violot are used to produce green, dark blue, maroon, and purple, respectively.

Phthalocyanine pigments are the most popular source of pigments for use in green

and blue paints. Phthalocyanine blue pigments cover a wide range of shades from greenish

blue to reddish blue, while phthalocyanine green pigments can range from bluish green to

yellowish green (Herbst and Hunger, 2004). Despite the range and popularity of

phthalocyanine pigments in producing many shades of blue and green, they are incapable of

producing shades of violet. Violet consists of wavelengths between 400-435 nm, which is

adjacent to blue (435-480 nm) on the visible spectrum. Carbazole violet, the pigment used in

purple, is not only capable of producing various shades of violet, but can also be used to

impart a bluish tint to red paint as well as a reddish tint to blue paint. It is also an important

13

pigment used to mask the slight yellow undertone commonly encountered with the TiO2

pigments (Herbst and Hunger, 2004).

Organic sources typically have the capacity to absorb more light than they reflect as

well as have higher tinting strength and color purity (Stoye and Freitag, 1998). For these

reasons, organic pigment sources are often combined with inorganic sources to produce

colors that either alone cannot. Colors that contain both organic and inorganic pigment

sources include light blue (phthalocyanine blue; TiO2) and yellow (pyrazolone orange;

yellow Fe2O3).

The extremely high absorption of light throughout the visible spectrum is

characteristic of all black pigments, including carbon black. Absorption of light by black

pigments can reach up to 99.8%, including infrared and ultraviolet light (Buxbaum and Pfaff,

2005). The ability of black pigments to absorb an extremely high percentage of visible light

is further shown by the low percentage of pigment needed in black paints, relative to the

amount of pigment needed in other colors.

Experimental Methods

There is currently little known information about how these various pigments and

colors affect turfgrass photosynthesis, transpiration, and canopy temperature. However, there

is a considerable amount of information available on more generally applied concepts and

proven methods that may be used to investigate athletic field paint and plant health. For

example, spectroradiometry measurements of light quality, portable gas exchange system

14

measurements of photosynthesis, and weighing lysimetry measurements of transpiration

losses have all been well-documented in previous turfgrass research.

Photosynthetically active radiation and the specific wavelengths of light that lie

within it are measured using radiometry techniques. Radiometry is defined as the

measurement of the properties of radiant energy and is often measured in Joules (J). The rate

of flow of radiant energy is referred to as the radiant flux and is often measured in watts (W),

where 1W = 1 J s-1

. Radiant flux can be measured as it flows from a source through one or

more reflecting, absorbing, or transmitting media (the earth’s atmosphere, plant canopy,

athletic field paint) to the receiving surface, which is often a photosynthesizing leaf (Biggs,

1984). Measurements of this radiant flux are defined by the wavelength(s) at which they are

measured and include all solar radiation (Irradiance; W m-2

), radiation between 400 and 700

nm capable of driving photosynthesis (PAR; W m-2

), or radiation at specific wavelengths (W

m-2

nm -1

). When measuring irradiance at specific wavelengths, the term spectral is added,

and thus spectral irradiance is defined as the irradiance at a given wavelength per unit time

and is measured using a technique called spectroradiometry.

Spectroradiometry can be used to measure the effects of athletic field paint on PAR,

as well as wavelengths within PAR, available for use in painted turfgrass canopies.

Specifically, the ability of various colors of athletic field paint to selectively reflect, transmit,

and absorb visible light can be examined using experimental techniques modified from

previous research. In a method described by Earl and Tollenaar (1997), reflection and

transmission of PAR through maize (Zea mays L.) leaves can be performed through the use

of an integrating sphere (LICOR 1800-12, LI-COR) and spectroradiometer (Apogee

15

Instruments). In this method, a maize leaf is placed on the exterior of the integrating sphere

while a light source is used to illuminate the sphere from different locations according to the

manufacturer’s instructions. After a series of measurements, reflection and transmission are

determined which allows for calculations of absorption using the equation: Sample

absorption = 1 – reflection – transmission.

Similar measurements can be performed on various colors of athletic field paint when

uniformly applied to transparency film (3M PP2500, 3M) using a wet film applicator

(Gardco 8-Path, Gardco). This device allows a small quantity of liquid to be applied to

surfaces at a known wet thickness for subsequent testing. The dried paint film can then be

placed on the exterior of the integrating sphere as described by Earl and Tollenaar (1997) to

determine the reflection, transmission, and absorption of PAR as well as wavelengths within

PAR that pass through various colors and thicknesses of athletic field paint. The two main

objectives of these types of measurements are to determine the ability of athletic field paint

to intercept PAR which would create a shading effect, and to determine the ability of paint to

differentially alter wavelengths within PAR in a color-dependent manner.

Any shading effect created by athletic field paints may have the potential to

negatively affect total canopy photosynthesis (TCP) rates in painted turfgrass canopies.

Reductions in photosynthesis have been documented in turfgrass research as a result of

applications of humic acids (Liu et al., 1998), plant growth regulators (Beasley and Branham,

2007; Gaussoin et al., 1997), and selective herbicides (Willard et al., 1990). However,

reductions in photosynthesis as a result of athletic field paint applications have not yet been

documented.

16

Total canopy photosynthesis is often measured in turfgrass systems using a portable

gas exchange system (LI-6400, LI-COR Inc.) connected to a transparent mylar or plexiglass

chamber (Singh et al., 2011; Willard et al., 1990; Bremer and Ham, 2005). This method is

performed by measuring the C exchange rate during the daytime in full light when

photosynthesis is actively occurring. In this method, C exchange rates are first measured in

full light in the growth chamber and then in total darkness immediately after the light

measurements are recorded (achieved by covering the plexiglass chamber with opaque black

fabric). Measured C exchange rates under dark conditions are considered to represent

canopy, root, and soil respiration. Total canopy photosynthesis (TCP) is then calculated by

adding the absolute value of dark respiration to the observed carbon exchange rate in the

light (Singh et al., 2011). Measurements of TCP using this method in painted and un-painted

turfgrass canopies could potentially provide insight into the extent to which TCP is reduced

by applications of athletic field paint.

While the interception of PAR by paint pigments is an area of study that may provide

insight into the impacts of athletic field paint on TCP, it is likely not the only factor

implicated in reductions of turfgrass quality in painted turfgrass canopies. As previously

mentioned, the ability of athletic field paint to impact gas exchange via transpiration is also

likely problematic for plant health. The impacts of various management practices and

environmental factors on turfgrass transpiration have been widely documented and include

nitrogen rate, mowing height, herbicide application, and soil composition (Barton et al.,

2009; Biron et al., 1981; Erickson and Kenworthy, 2011; Wherley and Sinclair, 2009; Miller,

2000.) as well as species and variety (McGroary et al., 2011; Beard et al., 1992.).

17

Transpiration, or evapotranspiration (ET), is often measured gravimetrically using

mass balance techniques in closed or open-system lysimeters. Lysimeters are commonly

considered the standard method for directly measuring evapotranspiration from plants in

agricultural systems (Payero and Irmak, 2007). When this is the primary point of interest,

weighing lysimeters are often the standard method for direct measurement. These lysimeters

measure crop evapotranspiration by measuring the change in soil mass from an isolated soil

volume over a specific amount of time. In turfgrass research, lysimeters are typically much

smaller than in agricultural crop research and are frequently made from materials like

polyvinyl chloride (PVC) or other plastics. These smaller lysimeters are sometimes referred

to as ‘microlysimeters’ (Bremer, 2003). The benefits of these smaller lysimeters are typically

lower cost and easier installation than their larger, agricultural counterparts.

However, one drawback to microlysimeters is that because they are not used in their

natural setting as agricultural lysimeters often are, it is sometimes difficult to uniformly apply

and compact soils to similar bulk densities in a manner that will not affect the objectives of

the research. One way to overcome this variability is by using consistent root-zone materials

including sand, sand/peat mixtures, or inorganic soil amendments like Profile, a porous

ceramic soil amendment (Profile Porous Ceramic Greens Grade, Profile). Profile has been

shown to produce high quality turfgrass in previous research regarding inorganic soil

amendments and is desirable for use in transpiration studies due to its uniformity and

adequate soil moisture retention (Miller, 2000). Feldhake et al. (1983) used microlysimeters

to demonstrate that water use increases in a linear manner with incident solar radiation.

However, paint is unique in the fact that it has the potential to confound the relationship

18

between incident solar radiation and transpiration through decreases in TCP, stomatal

obstruction, and changes in canopy temperature. If stomata are obstructed by paint, then

transpirational water loss would potentially decrease due to the inability of water vapor to

diffuse through the pigments and resin that remain on the leaf after application. Obstruction

of stomata could also lead to reductions in evaporative cooling and thus, increased canopy

temperatures.

The many questions presented in this review represent a vast area of research that has

yet to be conducted with regard to the impacts of athletic field paint on turfgrass health and

performance. Despite potential impacts, athletic field paints are a necessary component of

sporting events worldwide and will continue to be used. Therefore, a thorough understanding

of their impacts on turfgrass health is vital to mitigating injury and maintaining safe,

functional, and attractive athletic turf.

19

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24

ATHLETIC FIELD PAINT IMPACTS LIGHT SPECTRAL QUALITY AND

TURFGRASS PHOTOSYNTHESIS

William Casey Reynolds, Grady L. Miller,* and Thomas W. Rufty

Affiliation: Department of Crop Science, North Carolina State University, Campus Box

7620, Raleigh NC 27695.

Corresponding Author: [email protected]

Abbreviations: PAR, Photosynthetically active radiation; PMS, Pantone matching system;

TCP, Total Canopy Photosynthesis.

Published in Crop Sci. 52:2375-2384 (2012).

doi: 10.2135/cropsci2012.01.0059

Crop Science Society of America. 5585 Guilford Rd. Madison, WI 53711.

mailto:[email protected]

25

Abstract

Athletic field paints are applied to turf surfaces with little or no acute injury.

However, field managers notice chronic declines in turfgrass health after repeated

applications. This study examines athletic field paint impacts on spectral quality and

associated turfgrass photosynthesis. Growth chamber experiments evaluated effects of red

and white athletic field paint as well as one, two, three, and four repeated weekly applications

on total canopy photosynthesis (TCP) of perennial ryegrass (Lolium perenne L.). Paint

treatments were applied weekly for 6 wk with TCP recorded 24 h after each application using

a gas exchange system. Spectroradiometry experiments evaluated reflection, absorption, and

transmission of light at various wavelengths based on paint color, dilution, and thickness.

Over a six week period all treatments reduced TCP based upon color (P ≤ 0.0001) and

dilution (P ≤ 0.0001). Red no dilution paint produced a 75% reduction in TCP over 6 wk

while white 1:1 diluted paint only produced a 19% reduction. Spectroradiometry data

suggests this is likely due to reductions in photosynthetically active radiation (PAR) with red

paint absorbing 51% of incident PAR while transmitting and reflecting 6% and 43%,

respectively. White paint transmitted 5% of PAR while reflecting 95%. Alterations in light

spectral quality resulting from athletic field paint applications can impact PAR, which may

result in reduced turfgrass health.

26

Introduction

Athletic field paints are routinely applied to field surfaces for marking regulation

lines, logos, advertisements, etc. in sporting events worldwide. Manufacturers focus much of

their efforts on producing bright, distinct, uniform paints that are both affordable and non-

injurious to grass species commonly used on athletic field surfaces. Within the industry,

latex, water-based paints are some of the most commonly applied products. Latex paint

consists of four major components: pigments, resins, solvents, and additives. Each of the

components provides a different function within paint chemistry, any of which may be

problematic for turfgrass health. Among these four components, pigments likely have the

most potential for damage, because one of the two primary roles of pigments is to create

opacity to hide or cover a surface (turfgrass leaves) by blocking visible wavelengths of light.

Pigments consist of dry powders and are dependent upon desired color. Common pigments in

white, black, and red paint are TiO2 (titanium dioxide), C, and Fe2O3 (iron oxide),

respectively. Each is very effective in blocking light, thereby providing the required opacity.

Pigments also provide color to paint through selective absorption of specific wavelengths,

which may lead to turfgrass damage by altering light intensity and spectral quality.

Athletic field paints are formulated with the intent that ingredients do not cause acute

injury when properly applied. However, field managers routinely notice turf injury from

repeated applications (G. Miller, unpublished data, 2011). Although the cause(s) of the

damage is unknown, a potential explanation lies in secondary, chronic effects on plant

growth processes. One important plant process that is likely impacted by repeated paint

applications is photosynthesis. Pigments may block specific wavelengths of light in the

27

visible spectrum and reduce photosynthetically active radiation (PAR) at leaf surfaces.

Visible light and PAR share the same range of wavelengths, from 400-700 nm. Within PAR,

there are also particular spectral bands that are most effectively absorbed for photosynthesis.

These bands are often grouped by color; blue light is considered to be 400-500 nm and red

light is considered to be 600 to 700 nm (Taiz and Zeiger, 2006). Chlorophyll a is known to

have peak spectral absorption at 410, 430, and 660 nm while peak absorption for chlorophyll

b occurs at 430 and 640 nm (Taiz and Zeiger, 2006). Paint pigments designed to alter

visible light in order to produce a specific color may also potentially alter reflection,

transmission, and absorption of PAR available for photosynthesis within turfgrass canopies.

The impacts of reduced light quantity and altered light quality on turfgrass growth

have been examined in studies of shading from trees, buildings, and weeds (Bell et al., 2000;

Gaskin, 1965; McKee, 1963). Reductions and alterations in light also have been linked to

reductions in turf performance as well as physiological changes within grasses (McBee,

1969; Dudeck and Peacock, 1992; Wilkinson and Beard, 1975). Up to this time, however, no

such studies have been conducted with paint applied to turfgrass.

This study was initiated to investigate the underlying processes responsible for

declining turfgrass health with repeated painting. Using red and white paint, lab experiments

first examined impacts on PAR as a result of selective color reflection, transmission, and

absorption by pigments. Subsequent growth chamber experiments then examined how these

impacts related to turfgrass photosynthesis.

28

Materials and Methods

Spectroradiometry Experiments

An experimental system was designed to quantify reflection, transmission, and

absorption of PAR by red and white paint. Paint treatments were uniformly applied to

transparency film (3M PP2500, 3M) using a wet film applicator (Gardco 8-Path, Gardco).

The device allowed a small quantity of liquid to be applied to surfaces at a known wet

thickness for subsequent testing. Paint at no dilution and a 1:1 dilution with water was

applied at a uniform wet thickness of 0.125, 0.250, 0.375, 0.500, 0.625, or 0.750 mm. The

final dried thickness of each film was recorded using a digital micrometer to ensure

uniformity.

Reflection and transmission of light through the paint was measured between 400 and

700 nm at 0.5-nm intervals using an integrating sphere (LICOR 1800-12, LI-COR) and

spectroradiometer (Apogee Instruments). Measurements were performed on each of the six

wet thicknesses. The reflection reference was newly pressed BaSO4 (barium sulfate). The

painted side of the transparency film faced the inside of the integrating sphere for the

reflection reference and sample readings. For transmission sample and reference readings,

the painted side of the transparency film faced the outside of the integrating sphere. The light

source used to illuminate the integrating sphere was constant, but its location within the

sphere varied between reference and sample readings as well as between reflection and

transmission readings. Sample absorption was calculated as sample absorption = 1 –

reflection – transmission. Data were used to calculate regression equations that described

percent incident PAR reflected, transmitted, and absorbed at the various thicknesses.

29

Narrowband and broadband spectral data were collected at specific wavelengths to

determine effects on light quality. The narrowband wavelengths were 410, 430, 640, and 660

± 10 nm, and the broad-band wavelengths were blue (400-500 nm), red (600-700 nm), and

PAR (400-700nm). To remove thickness as a potential confounding variable, a uniform

thickness of 0.050 mm dried thickness was selected from the six levels of wet thickness

previously mentioned. This dried thickness was obtained using 0.250 mm wet thickness for

the red no dilution, red 1:1 dilution, and white 1:1 dilution treatments, and a 0.125 mm wet

thickness for the white paint treatment with no dilution. The resulting 0.050 mm dried

thicknesses (3 replications) were not different using Fischer’s protected LSD test at α <0.05.

Measurements of reflection and transmission, and calculations of absorption were determined

as previously mentioned using the integrating sphere and spectroradiometer.

Growth Chamber Experiments

The research was conducted at the Southeastern Plant Environment Laboratory at

North Carolina State University in Raleigh, NC. Sixty pots were prepared with a 50:50 v/v

sand and peat substrate based on the original “Cornell Mix” (Boodley and Sheldrake, 1972).

The substrate was steam-sterilized, placed into 15.8-cm diameter pots, and seeded on 19 Feb.

2009 with ‘Palmer V’ perennial ryegrass at a rate of 55 g m-2. Perennial ryegrass was

selected due to its widespread use as an overseeding crop on bermudagrass (Cynodon spp.)

athletic fields. After seeding, the pots were placed into a growth chamber maintained at

22/18oC (day/night) with a 9-hr photoperiod (0730 to 1620 h) and a photosynthetic photon

flux density of 650 µmol m-2 s-1 provided by a combination of incandescent and fluorescent

30

lamps. Water and nutrient solution were applied twice daily throughout the ryegrass

establishment period and then once daily during experimental periods. The “standard nutrient

solution” is described in detail in the North Carolina State University Phytotron Procedural

Manual (NCSU, 2011). After initial establishment, all pots (experimental units for both

studies) were re-seeded two additional times on 6 and 16 Mar. 2009 at 55 g m-2 to ensure a

dense, uniform turf canopy prior to application of paint treatments. Pots were mowed twice

weekly at 2.5 cm using a handheld shear (194380 Oster Showmaster).

Paint Application

Before application of paint treatments, turf in all sixty pots was allowed to reach

maturity and then experimental units were randomly divided into two sets, each for a

separate study . The first study (hereafter referred to as “Study 1”) began on 27 May 2009

and consisted of six weekly applications of two colors (red and white), two dilutions of each

(no dilution and 1:1 dilution with water), and an un-painted control. The second study

(hereafter referred to as “Study 2”) began on 3 June 2009 and consisted of weekly

applications of red non-diluted paint for 1, 2, 3, or 4 wk, as well as an un-painted control. In

Study 2, all treatments received paint applications during week one, then three treatments

during week two, two treatments during week three, and one treatment during week four.

Red non-diluted paint was selected for Study 2 due to it having the most negative impacts on

photosynthesis during Study 1. Both studies were repeated over two 6x-wk experiments

(hereafter referred to as Exp. 1 and 2), and treatments in each experiment had three

replications. In both studies, Exp. 2 began one week after the conclusion of Exp. 1. All paint

31

treatments consisted of Pioneer Brite Stripe Airless paint (Pioneer Athletics). The Pantone

Matching System (PMS), a standardized color reproduction system, was used to define the

red treatment as PMS 186. The 1:1 dilution treatment was a 1:1 volumetric dilution of paint

and water. Paint treatments were applied using a CO2-pressurized sprayer with flatfan

nozzles (Teejet8004VS, Teejet Spraying Systems Co.) calibrated to apply approximately 168

L ha-1. This rate was achieved by four applications in multiple directions to each pot, which

ensured uniform coverage of turfgrass leaves.

Photosynthesis Measurements

Carbon exchange rates were measured in Study 1 24 h after each of six weekly paint

applications as well as 3 wk after all paint applications ceased. In Study 2, C exchange rates

were measured 25 h after each of four paint applications as well as 1 and 2wk after all paint

applications ceased. Carbon exchange rates were determined by enclosing the turfgrass

canopy in a transparent plexiglass chamber (956.42cm3) connected to a portable gas

exchange system (LI-6400, LI-COR Inc.). Measurements of C exchange rate were always

taken between 1000 and 1500 h. Carbon exchange rates were measured in full light in the

growth chamber and in total darkness immediately after light measurements were recorded

(achieved by covering the plexiglass chamber with opaque black fabric). Measured C

exchange rates under dark conditions were considered to represent canopy, root, and soil

respiration. Total canopy photosynthesis (TCP) was calculated by adding the absolute value

of dark respiration to the observed carbon exchange rate in the light (Singh et al., 2011).

Canopy temperature was measured immediately prior to enclosure of the turfgrass in the

32

transparent plexiglass chamber using an infrared digital thermometer (Fluke 63IR, Fluke

Inc.).

Statistical Analysis

Data from spectroradiometry and growth chamber experiments were subjected to

ANOVA to determine treatment effects. TCP and canopy temperature data showed

significant treatment effects but also showed interactions with experiment. Therefore, growth

chamber data from both 6-wk experiments within Study 1 and Study 2 were analyzed and

presented separately with treatment x experiment interactions reported in appropriate

ANOVA tables. Treatments within all experiments were subjected to Fischer’s Protected

LSD test at the 0.05 probability level when F-tests indicated significant treatment effects.

Orthogonal contrasts were produced for analysis of reflection, transmission, and absorption

of PAR averaged over six wet-applied paint thicknesses. Orthogonal polynomials were used

to produce regression curves for analysis of reflection, transmission, and absorption of PAR.

Only highest-order interactions (quadratic or cubic) for each treatment were reported.

Orthogonal contrasts also were produced to compare treatment effects on net canopy

photosynthesis and canopy temperature in growth chamber experiments.

Results

Spectroradiometry Experiments

The ability of paints to reflect, transmit, and absorb PAR was found to be different (P

≤ 0.0001) when averaged over six wet thicknesses and based on orthogonal contrasts (Table

33

1). Differences also were found between and within paint treatments (color and dilution).

Red 1:1 dilution and red no dilution paint reflected the least amount of PAR at 41.8 and

42.9%, respectively, while the white paint treatments reflected much higher amounts (94.5

and 97.0%). A small difference in absorption of PAR was seen between the red treatment

(52.7%) and when it was diluted (48.5%), while no absorption was found in either treatment

of white paint. Differences in transmission of PAR were less dramatic, although still

significant, with the highest amount transmitted through red 1:1 dilution (9.7%) and the

lowest through white paint with no dilution (3.0%).

Regression plots revealed that with increasing thickness, the percent transmitted

decreased rapidly to minimal levels (Fig. 1; Table 2). As seen with results in Table 1,

reflection of PAR was always higher for white paint compared to red paint over all six wet

thicknesses, while absorption by red was always higher than white.

The narrow- and broadband experiments also illustrate the highly reflective

characteristics of white paint when measured at a uniform dried thickness (Table 3).

Narrowband data indicate reflection of PAR by white paint and diluted white paint is

between 94.4 and 100% at wavelengths of 430, 640, and 660 nm. Reflection was slightly

lower at 410 nm, being 80.9%. As expected from the PAR results above, red paint

treatments had higher absorption at all broad and narrow-band wavelengths. Red non-diluted

and 1:1 diluted paint exhibited a capacity for increased absorption of PAR compared to white

where red non-diluted paint absorbed 45.0% PAR at 0.125 mm wet thickness and 55.9%

PAR at 0.75 mm wet thickness (Fig. 1). Likewise, red 1:1 diluted paint absorbed 41.8 and

53.1%, respectively, at the same thicknesses. Narrow- and broadband wavelength data

34

support PAR data as well as indicate red paint’s ability to selectively absorb various

wavelengths within PAR. Red non-diluted and diluted treatments exhibited high absorption

at 410 and 430 nm by absorbing 90.2 and 91.0%, respectively, at these wavelengths.

However, at 640 nm red non-diluted paint only absorbed 12.8% of light along with 12.4% at

660 nm. This absorption was further reduced in red 1:1 diluted paint to 4.0 and 4.5%.

Reflection of PAR by red non-diluted paint was 70.9% in the 600-700 nm red

broadband wavelengths while only reflecting 8.0% of light in the blue broad-band

wavelengths. Narrowband wavelength data also indicate that more light is reflected in the

640 and 660 nm wavelengths than the 410 and 430 nm wavelengths as a result of red paint.

The 640 and 660 nm wavelengths reflected 75.9 and 75.2% of light, respectively, while the

410 and 430 nm wavelengths only reflected 9.7 and 8.9%.


Study 1

Reductions in TCP as a result of all paint treatments were documented and were

consistent over both 6-wk experiments (P ≤ 0.0001) despite an interaction between treatment

and experiment (P ≤ 0.0006) as indicated by ANOVA (Table 4). Red no-dilution paint

produced the greatest reduction in TCP followed by red 1:1 dilution, white no dilution, and

white 1:1 dilution, respectively (Table 5). Red no-dilution paint reduced TCP by 75% in Exp.

1 and by 79% in Exp. 2. Red 1:1 dilution paint reduced TCP by 48% and 54%, in Exp. 1 and

2, respectively while white paint treatments were less injurious. Orthogonal contrasts indicate

the importance of both color and dilution on TCP in both experiments (P ≤ 0.0001). Red

35

paint was more damaging to TCP than white paint, although diluting each color reduces these

negative effects. An orthogonal contrast used to compare TCP of all paint treatments to the

un-painted control was also significant (P ≤ 0.0001).

In addition to decreases in TCP, increases in canopy temperature were also significant

among paint treatments (P ≤ 0.0001) with the highest increase in temperature resulting from

red no-dilution paint in both experiments (Table 5). Furthermore, red 1:1 dilution, white no-

dilution and white 1:1 dilution all increased temperatures relative to the control in Exp. 1, but

only red 1:1 dilution produced further increases in canopy temperatures in Exp. 2. In

reference to canopy temperature, dilution did not affect canopy temperature whereas paint

and color had an impact in both experiments.

Study 2

Red no-dilution paint was selected for use in Study 2 due to its ability to cause the

highest reductions in TCP during Study 1. In Study 2, repeated applications of red no-

dilution paint that were applied for 1, 2, 3, or 4 wk were found to produce reductions in TCP

as well as increases in canopy temperature that were most strongly attributed to treatment

effects (P ≤ 0.0001) as indicated by ANOVA (Table 6). Date, experiment, and treatment

interactions with each also contributed to the model. In both experiments, each additional

week that red non-diluted paint was applied resulted in further decreases in TCP over the

entire six week experiment (Table 7). One, two, three, and four applications of red non-

diluted paint resulted in 12, 24, 37, and 53% reductions, respectfully in TCP during Exp. 1

and results were similar results in Exp. 2.

36

To assess the ability of perennial ryegrass to recover after application of paint

treatments ceased, TCP data for each treatment were normalized to the control for weeks one

through six and presented in Fig. 2. In each treatment, photosynthetic recovery began within

1 wk after final application of one, two, three, or four paint treatments. Perennial ryegrass

subjected to only one application of red no-dilution paint was able to achieve 84% of TCP

compared to the untreated control within 1 wk after application and up to 94% recovery by 3

and 4 wk after the last application. Further applications of red no-dilution paint resulted in

less photosynthesis recovery. At week six, for example, perennial ryegrass receiving one,

two, and three applications of paint recovered to TCP rates similar to the control while

perennial ryegrass receiving four applications was only able to recover to 84% of the

untreated control.

Discussion

Spectroradiometry

A primary objective of this study was to examine the impact of athletic field paint on

PAR. Varying effects on PAR and net canopy photosynthesis as a result of painting are a

direct result of paint chemistry and pigment composition. Red and white athletic field paints

differ fundamentally in their pigment source, with white paint being composed primarily of

TiO2 pigments while red paint is composed primarily of Fe2O3 pigments. These pigments

produce different colors due to their varying ability to reflect, transmit, or absorb PAR at

specific wavelengths. Titanium dioxide is widely used as a white pigment due to its superior

light-scattering properties over all wavelengths in the visible spectrum (Buxbaum and Pfaff,

2005). Alternatively, light-scattering by colored pigments, such as red, is much more

37

wavelength dependent. Red Fe2O3 reflects approximately 20 to 30% more visible light in the

600-700 nm range than in the remaining wavelengths of the visible spectrum (Endrib, 1998),

an effect shown in the broad- and narrowband data in Table 3, which produces the

characteristic red color.

The importance of color in altering PAR is clearly shown in our data sets.

Orthogonal contrasts (P ≤ 0.0001) illustrate the effects of color on PAR (Tables 1 and 2)

while treatment effects (P ≤ 0.0001) illustrate the effects of color on broad- and narrowband

wavelengths (Table 3). Furthermore, broad- and narrowband wavelength data are consistent

with PAR data in that much larger amounts of PAR are reflected by white paint treatments

than red paint treatments over all wavelengths.

Reflection of PAR by white no-dilution paint was so large at 640, 660, and 600-700

nm that it produced summed values of reflection, transmission, and absorption of PAR

exceeding 100%. The likely explanation for values exceeding 100% lies in the higher

refractive index of TiO2 relative to BaSO4. As the refractive index increases, so does the

ability of a pigment to scatter light. Two TiO2 pigments commonly used in paints are rutile

and anatase, which have refractive indices of 2.80 and 2.55, respectively. Barium sulfate,

which makes up the interior wall of the Licor 1800-12 integrating sphere only has a

refractive index of 1.64 (Buxbaum and Pfaff, 2005). Therefore, the highly reflective nature

of TiO2 produced reflection readings near or greater than 100% while still transmitting light

in the 640, 660, and 600-700 nm range.

The methodology used for measurements of narrowband effects influenced the

absolute values for reflection and transmittance of white paint. Data indicate that wet

38

thicknesses of white non-diluted paint dried much thicker than similar wet thicknesses of red

paint (Fig. 3). Paints are fundamentally different due to varying sources and amounts of

pigments required to produce different colors. White paint possesses a much higher

percentage of pigment solids than red paint and therefore dries thicker. (G. Sajner, personal

communication, 2011). The wet thickness selected for the white non-diluted treatment was

0.125 mm whereas wet thicknesses for other treatments were 0.250 mm. When dried, each of

these produced a uniform dried thickness of 0.050 mm for comparison. The 0.125 and 0.250

mm wet thicknesses were among the thinnest treatments produced for observation, so it is not

surprising these thicknesses would transmit light. However, it is worth noting that PAR data

collected over all six wet thicknesses and averaged together resulted in reflection,

transmission, and absorption values that summed to 100%, as expected.

Differences in transmission over broad and narrow-band wavelengths based on color

were small and in most cases insignificant. The largest difference over any measured

wavelength was recorded in the broad-band wavelength 400 to 700nm where transmission of

PAR through red 1:1 dilution paint was 14.8% while transmission through white no-dilution

paint was only 4.7%. However, as indicated in Fig. 1, transmission of light through paint

decreases as paint thickness increases. Athletic field managers routinely apply paint at high

levels of thickness to achieve uniform coverage as well as bright, distinct lines and logos. As

a result of this, transmission of PAR likely has much less potential impact on turfgrass

photosynthesis than either reflection or absorption.

39

Impacts on Photosynthesis

The second objective of this study was to determine if alterations in PAR and light

spectral quality were sufficient to affect TCP of perennial ryegrass. As previously mentioned,

results from growth chamber experiments indicate that alterations and reductions in PAR, as

well as broad- and narrowband wavelengths, have the capacity to reduce TCP of perennial

ryegrass. The high absorption of PAR by red paint, coupled with extremely high reflection of

PAR by white paint result in dramatic differences in available PAR within the turfgrass

canopy. Previous research with crop plants has shown that available PAR can be altered by

reflection from various colors of paint and is sufficient to affect plant growth. Kasperbauer

(2000) found that upwardly reflected light from painted plastic covers beneath cotton

(Gossypium hirsutum L.) canopies differed by color. Plants grown over plastic surfaces

painted white received substantially more PAR than plants grown over plastics painted red

and green. In a separate study, it was found that carrots (Daucus carota L.) grown over plastic

mulches painted white, yellow, red, blue, and green received varying amounts of reflected

PAR (Antonious and Kasperbauer, 2002). As in our experiments, white mulches reflected

substantially more PAR than red mulches. The PAR that is reflected within the turfgrass

canopy by pigments is likely still available for absorption by chlorophyll in areas with

cracked leaf surfaces or partial paint coatings and on abaxial leaf surfaces or lower portions

of the canopy that may not have received paint. Furthermore, as turfgrasses grow and

remaining pigments are mowed off, increased reflectance of light by white paint can be

useful for photosynthesis by newly formed leaves. This increased reflection of PAR by white

40

paint relative to red paint is likely responsible for the smaller reductions in TCP found in

growth chamber Study 1.

The absorption of PAR by pigments in red paint has the potential to reduce TCP, an

analogous effect to that of shading. Shade is typically considered to be a result of light

interception by trees, structures, or weeds. However, light that is intercepted and absorbed by

paint pigments can also produce reductions in available PAR, as indicated by our

spectroradiometry experiments. Decreased turfgrass growth as a result of reductions in PAR

has previously been reported. Baldwin et al. (2009) found that shade fabrics filtering

wavelengths 360 to 720 nm produced clipping yields of only 21.4% of treatments receiving

no shade. Similarly, in our experiments, red paint treatments absorbed 50.6% more PAR than

white paint treatments which resulted in much lower rates of net canopy photosynthesis. Also

in the Baldwin et al. (2009) study, shade fabrics that selectively filtered wavelengths of light

within PAR reduced growth. For example, shade fabrics filtering wavelengths 560 to 720

nm, yet allowing passage of blue light (400 to 500 nm) for 6 wk, resulted in clipping yields

of ‘Tifway’ bermudagrass [Cynodon dactylon (L.) Pers. X Cynodon transvaalensis Burtt-

Davy] that were only 38.2% of control. Shade cloths filtering 360 to 520 nm and 360 to 560

nm while allowing passage of red light (600 to 700 nm) also reduced clipping yields.

Spectroradiometry experiments conducted in our study show that absorption of blue light in

broad- and narrowband wavelengths was particularly high for red paint treatments due to the

selective nature of the Fe2O3 pigments. Red no-dilution paint absorbed 90.2, 91.0, and

91.9% of blue light at 410, 430, and 400-500 nm, respectively. The absorption of PAR, as

well as light in selective broad and narrow-band wavelengths produces a similar effect to

41

shading because the quantity and quality of light has been reduced through absorption by

paint pigments. Any light absorbed by these pigments is no longer available for use by plants

and can produce reductions in TCP seen in the growth chamber experiments.

Results from growth chamber Study 2 indicate the chronic nature of the red non-

diluted effects. The ability of TCP to recover from the painting decreased as application

number increased. Reductions in turfgrass performance over time as a result of excessive

shade have been routinely documented. In the Baldwin et al. (2009) study, turfgrass quality

and clipping yield of bermudagrass and zoysiagrass (Zoysia matrella (L.) Merr.) also

decreased as duration of shade increased. Reductions in traffic tolerance were observed in

several bermudagrass and zoysiagrass cultivars as the time under shade and number of traffic

applications increased (Trappe et al., 2011). The notion that reductions in turfgrass quality

and performance are caused by chronic shading by athletic field paint applications is

consistent with athletic field paints not being acutely toxic to turfgrasses. Also, anecdotal

evidence from professional athletic field managers indicates that decreased growth and

density from athletic field paint applications are usually noticed only after multiple painting

events. These decreases become more severe as the number of paint applications increase.

To fully understand the capacity pigments have to affect turfgrass photosynthesis, it is

important to understand the role that pigments play in paint relative to the other ingredients

(resins, solvents, and additives). Pigments are dispersed into the resin portion of the paint,

which provides adhesion for the paint to stick to turfgrass leaves. Solvents are then used to

dilute the paint as well as provide uniformity in application thickness. Additives often serve

as wetting agents that help incorporate the dry pigments into the liquid paint as well as

42

surface tension modifiers that aid in coating the leaf surface. Once the paint is applied, the

solvent evaporates leaving a dried paint film on the leaf surface that is made up primarily of

pigments. As such, pigments play the greatest role in alterations of PAR within the turfgrass

canopy and resulting photosynthesis because unlike the other three components of paint, they

remain in the turfgrass canopy after application.

Pigments present in athletic field paint have the capacity to reduce turfgrass growth

through the absorption of PAR that would otherwise be available for plant use. They also

have the capacity to alter spectral quality through selective reflection, transmission, and

absorption of various wavelengths within PAR. Photosynthetically active radiation, broad-

band, and narrow-band spectroradiometry data support the theory that TCP can be affected

by these alterations and reductions in light spectral quality and quantity as a result of paint

color, thickness, and dilution. This data suggests that potential exists for paint manufacturers

to identify and use pigments that are more selective in their ability to reflect specific

wavelengths necessary to produce a certain color while not excessively absorbing other

wavelengths useful for photosynthesis. It also suggests that field managers may alter their

painting habits, especially with darker, more injurious colors, to lower rates and raise dilution

factors to still allow for active turfgrass photosynthesis. However, the delicate balance

between producing bright, distinct logos and preserving turfgrass health is one that field

managers need to dictate based on their individual situation.

There is need for further exploration into the impacts of athletic field paint on

turfgrass photosynthesis and growth including the evaluation of additional colors, products,

rates, and timings. Athletic field paint applications are a necessary component of popular

43

athletic events worldwide and establishing the relationship between paint and turfgrass health

not only has the potential to improve the safety and aesthetics of athletic turf, but also the

potential to fundamentally change the nature of paint products themselves.

44

References

Antonious, G.F. and M.J. Kasperbauer. 2002. Color of light reflected to leaves modifies


Baldwin, C.M., H.Liu, L.B. McCarty, H. Luo, C.E.Wells, and J.E. Toler. 2009. Impacts of





Boodley, J.W. and R. Sheldrake. 1972. Cornell peat-lite mixes for commercial plant growing.

Ext. Info. Bul. 43. Cornell University.

Buxbaum, G. and G. Pfaff. 2005. Industrial inorganic pigments. WILEY-VCH Verlag GmbH

& Co. KGaA, Weinheim.

Dudeck, A.E. and C.H. Peacock. 1992. Shade and turfgrass culture. p. 269-284. In: D.V.

Waddington et al. (editors) Turfgrass ASA Monogr. 32. ASA, CSSA, and SSSA,

Madison, WI.


Germany.

Gaskin, T.A. 1965. Light quality under saran shade cloth. Agron. J. 57:313-314.





45

McKee, G.W. 1963. Use of a color temperature meter to characterize light quality in the

field. Crop Sci. 3:271-272.

NCSU Phytotron Procedural Manual. 2011. North Carolina State University Technical

Bulletin 244. (http://www.ncsu.edu/phytotron/manual.pdf.) North Carolina State

University, Raleigh, NC, USA (Accessed 15 May 2012.)





ed. Sinauer Associates, Sunderland,MA.

Trappe, J.M. , D.E. Karcher, M.D. Richardson, and A.J. Patton. 2011. Shade and traffic


Wilkinson, J.F. and J.B. Beard. 1975. Anatomical responses of ‘Merion’ Kentucky bluegrass

and ‘Pennlawn’ red fescue at reduced light intensities. Crop Sci. 15:189-194.

http://www.ncsu.edu/phytotron/manual.pdf

46

Table 1. Reflection, transmission, and absorption of photosynthetically active radiation (400-

700nm) by red and white paint averaged over six wet thicknesses (0.125, 0.250, 0.375, 0.500,

0.625, and 0.750 mm) using an integrating sphere and spectroradiometer.

Treatment Reflection Transmission Absorption

%

Red no dilution 42.9 c†

4.4 bc 52.7 a

Red 1:1 dilution 41.8 c 9.7 a 48.5 b

White no dilution 97.0 a 3.0 c 0.0 c

White 1:1 dilution 94.5 b 5.5 ab 0.0 c

Analysis of variance

Treatment *** *** ***

Orthogonal contrasts

Red no dilution vs. 1:1 dilution *** *** ***

White no dilution vs. 1:1 dilution *** *** ***

Red vs. white *** *** ***

***Significant at the 0.001 probability level

†Means within columns followed by the same letter are not significantly different according

to Fisher’s Protected LSD (P=0.05)

47

Table 2. Intercepts, linear, quadratic, cubic coefficients and standard error for regression equations of

reflection, transmission, and absorption of photosynthetically active radiation (PAR) (400-700nm) by red

and white paint at six wet thicknesses (0.125, 0.25, 0.375, 0.5, 0.625, and 0.75 mm) using an integrating

sphere and spectroradiometer.

PAR Treatment r2 Intercept

Coeffecients (SE)

Linear Quadratic Cubic

Reflection Red no dilution 0.986 33.78 (1.15) 7.36 (1.31) -1.69 (0.42) 0.13 (0.03)

Red 1:1 dilution 0.981 32.80 (0.97) 4.31 (0.63) -0.40 (0.08)

White no dilution 0.995 89.32 (0.53) 6.21 (0.61) -1.45 (0.19) 0.11 (0.01)

White 1:1 dilution 0.981 71.88 (3.60) 16.98 (4.20) -3.72 (1.34) 0.26 (0.12)


Red no dilution vs. red 1:1 dilution *** NS† *

White no dilution vs. white 1:1 dilution *** *** ***

Red vs. white *** *** ***

Transmission Red no dilution 0.998 28.23 (1.35) -17.03 (1.54) 3.57 (0.49) -0.25 (0.04)

Red 1:1 dilution 0.989 30.16 (1.80) -9.04 (1.18) 0.73 (0.16)

White no dilution 0.999 16.25 (0.19) -8.50 (0.22) 1.67 (0.07) -0.11 (0.01)

White 1:1 dilution 0.994 30.96 (2.79) -14.86 (3.18) 2.75 (1.02) -0.18 (0.09)


Red no dilution vs. red 1:1 dilution *** *** ***

White no dilution vs. white 1:1 dilution *** *** NS

Red vs. white *** *** **

Absorption Red no dilution 0.999 37.97 (0.21) 9.67 (0.24) -1.88 (0.07) 0.13 (0.01)

Red 1:1 dilution 0.995 39.52 (1.84) 1.62 (2.09) 0.69 (0.67) -0.09 (0.06)

White no dilution 0.984 0.73 (0.50) -1.04 (0.57) 0.36 (0.18) -0.02 (0.01)

White 1:1 dilution 0.976 -0.37 (0.24) 0.56 (0.27) -0.23 (0.08) 0.03 (0.01)


Red no dilution vs. red 1:1 dilution *** *** ***

White no dilution vs. white 1:1 dilution *** NS NS

Red vs. White *** *** NS

* Significant at the 0.05 probability level.

** Significant at the 0.01probability level.

***Significant at the 0.001 probability level.

†NS, not significant at P ≤ 0.05

48

Table 3. Reflection, transmission, and absorption of light at narrow-band and broad-band wavelengths by red no dilution, red 1:1 dilution,

white no dilution, and white 1:1 dilution paint when applied to transparency film at 0.050mm dried thickness.

Narrowband Broadband

PAR† Treatment 410 nm 430 nm 640 nm 660 nm 400-700 nm 400-500 nm 600-700 nm

% %

Reflection Red no dilution 9.74 c‡

8.95 b 75.97 b 75.22 b 43.64 c 8.01 d 70.94 b

Red 1:1 dilution 10.28 c 9.55 b 67.92 c 66.47 c 39.96 d 8.58 c 63.85 c

White no dilution 80.91 a 95.02 a 100.26 a 100.18 a 95.27 a 91.68 a 97.64 a

White 1:1 dilution 79.46 b 94.40 a 100.23 a 100.04 a 92.98 b 90.93 b 97.35 a


Treatment *** *** *** *** *** *** ***

Transmission Red no dilution 0.02 b 0.01 b 11.17 b 12.37 b 5.76 c 0.01 b 10.56 b

Red 1:1 dilution 0.02 b 0.02 b 28.04 a 29.04 a 14.87 a 0.01 b 26.73 a

White no dilution 0.84 a 3.81 a 10.89 b 11.01 b 4.72 d 4.86 a 10.64 b

White 1:1 dilution 1.08 a 4.36 a 11.45 b 11.54 b 7.01 b 5.39 a 11.15 b


Treatment *** *** *** *** *** *** ***

Absorption Red no dilution 90.23 a 91.04 a 12.84 a 12.40 a 50.59 a 91.98 a 18.48 a

Red 1:1 dilution 89.69 a 90.42 a 4.03 b 4.47 b 45.12 b 91.40 a 9.41 b

White no dilution 18.24 c 1.17 b NC‡

NC 0.00 c 3.44 b NC

White 1:1 dilution 19.45 b 1.23 b NC NC 0.00 c 3.66 b NC


Treatment *** *** *** *** *** *** ***

***Significant at the 0.001 probability level.

†PAR, photosynthetically active radiation.

‡Means within columns followed by the same letter are not significantly different according to Fisher’s Protected LSD (P=0.05)

§ NC, not calculated. Absorption not calculated due to ability of white paint to reflect and transmit a sum >100%.

49

Table 4. Analysis of variance for perennial ryegrass photosynthetic response from

weekly applications of red and white paint (no dilution and 1:1 dilution) treatments and

unpainted control in a controlled environment growth chamber during two 6-wk

experiments at the Southeastern Plant Environment Laboratory in Raleigh, NC.


Source df Mean square F P > F

Treatment 4 513.2 857.6 <0.0001

Experiment 1 0.1 0.1 0.7682

Replication 2 0.1 0.1 0.9106

Date 5 11.5 19.3 <0.0001

Treatment x date 20 0.9 1.6 0.0540

Treatment x experiment 4 3.1 5.2 0.0006

50

Table 5. Perennial ryegrass total canopy photosynthesis and temperature responses from various paint applications treatments during two six-week

experiments at the Southeastern Plant Environment Laboratory in Raleigh, NC. Experiment 1 Experiment 2

Treatment

CER†

in light

CER

in dark

Total canopy

photosynthesis

Canopy

temperature

CER

in light

CER

in dark

Total canopy

photosynthesis

Canopy

temperature

µmol CO2 m-2

s-1

oC µmol CO2 m

-2 s

-1

oC

Untreated 8.7a‡

3.5 a 12.2 a 23.2 c 9.3 a 3.8 a 13.1 a 24.7 c

White 1:1 dilution 6.5b 3.3 a 9.8 b 24.0 b 6.3 b 3.7 a 10.1 b 24.7 c

White no dilution 3.4c 3.4 a 6.8 c 23.9 b 2.4 d 3.8 a 6.2 c 24.5 c

Red 1:1 dilution 3.4c 2.9 b 6.3 d 24.1 b 3.1 c 2.9 b 6.0 c 25.8 b

Red no dilution -0.3d 3.4 a 3.0 e 24.7 a -1.0 e 3.7 a 2.7 d 26.3 a

Analysis of Variance

Treatment *** *** *** *** *** *** *** ***

Date *** ** *** NS§ *** *** *** ***

Treatment x date *** * *** NS *** *** ** NS

Orthogonal Contrast

Paint vs. no paint *** *** *** *** *** * *** ***

Red vs. white *** ** *** *** *** *** *** ***

No dilution vs. 1:1 dilution *** ** *** NS *** *** *** NS


** Significant at the 0.01 probability level.


†CER, carbon exchange rate, where sum of CER in light and absolute value of CER in dark equal total canopy photosynthesis


§NS, not significant at P ≤ 0.05

51

Table 6. Analysis of variance for perennial ryegrass photosynthetic response due to

zero, one, two, three, or four weekly treatments of red non-diluted paint during two 6-

wk experiments in a controlled environment growth chamber at the Southeastern Plant

Environment Laboratory in Raleigh, NC.


Source df Mean square F P > F

Treatment 4 346.3 281.9 <0.0001

Experiment 1 47.2 38.4 <0.0001

Rep 2 3.2 2.5 0.0807

Date 5 140.2 114.1 <0.0001

Treatment x Date 20 29.7 24.2 <0.0001

Treatment x Experiment 4 7.2 5.9 0.0002

52

Table 7. Perennial ryegrass total canopy photosynthesis and temperature responses from 0, 1, 2, 3, or 4 applications of red no dilution paint

during two six-week experiments at the Southeastern Plant Environment Laboratory in Raleigh, NC.

Experiment 1 Experiment 2

Treatment

CER†

in light

CER

in dark

Total canopy

photosynthesis

Canopy

temperature

CER

in light

CER

in dark

Total canopy

photosynthesis

Canopy

temperature

µmol CO2 m-2

s-1

oC µmol CO2 m

-2 s

-1

oC

Untreated 9.5 a‡

3.7 a 13.2 a 23.5 c 9.5 a 3.9 a 13.5 a 22.2 c

One application 7.9 b 3.7 a 11.5 b 23.5 c 7.7 b 3.2 b 10.9 b 23.2 b

Two applications 6.7 c 3.2 b 10.0 c 23.9 bc 5.1 c 2.7 c 7.9 c 23.3 ab

Three applications 4.9 d 3.2 b 8.2 d 24.2 ab 3.9 d 2.7 c 6.6 d 23.2 b

Four applications 3.3 e 2.7 c 6.1 e 24.3 a 2.4 e 2.4 d 4.9 e 23.9 a


Treatment *** *** *** ** *** *** *** ***

Date *** *** *** *** *** *** *** ***

Treatment x date *** NS *** *** *** *** *** *


** Significant at the 0.01 probability level.

***Significant at the 0.001 probability level. †CER, carbon exchange rate, where sum of CER in light and absolute value of CER in dark equal total canopy photosynthesis


NS, not significant at P ≤ 0.05

53

Figure 1. Reflection (a), transmission (b), and absorption (c) of photosynthetically active

radiation (400-700nm) of red non-diluted, red 1:1 diluted, white non-diluted, and white

1:1 diluted paint when applied to transparent film at six wet thicknesses (0.125, 0.250,

0.375, 0.500, 0.625, and 0.750 mm). Each data point is the mean of three replicates. Scales

for each y-axis are based on minimum and maximum percent photosynthetically active

radiation for each observation.

54

Figure 2. Normalized photosynthetic rates of perennial ryegrass measured 24 h after zero,

one, two, three, or four successive weekly applications of red non-diluted paint in a

controlled environment growth chamber at the Southeastern Plant Environment

Laboratory in Raleigh, NC. Data points at weeks five and six were collected 1 and 2 wk,

respectively, after the last paint application.

55

Figure 3. Dried thickness of paint treatments applied at 0.125, 0.250, 0.375, 0.500, 0.625, and

0.750 mm wet thickness. Standard Error (SE) is for the treatment mean of each applied wet

thickness.

56

ATHLETIC FIELD PAINT DIFFERENTIALLY ALTERS LIGHT SPECTRAL

QUALITY AND BERMUDAGRASS PHOTOSYNTHESIS

William Casey Reynolds, Grady L. Miller,* and Thomas W. Rufty


7620, Raleigh NC 27695.




Accepted by Crop Sci. on 22 April, 2013.

Crop Science Society of America. 5585 Guilford Rd. Madison, WI 53711.


57

Abstract

Painting of athletic fields is widespread throughout the world and can often cause

declines in turfgrass health. Visible light and photosynthesis share the same wavelengths

(400-700 nm), and it was hypothesized that alterations in visible light to produce specific

colors would lead to reductions in photosynthetically active radiation (PAR) and total canopy

photosynthesis (TCP). Lab experiments using a spectroradiometer and LICOR 1800-12

integrating sphere examined the impacts of ten colors of athletic field paint on PAR as well

as wavelengths within PAR. These colors were then applied weekly for five weeks to

‘Tifway’ bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy], and

TCP was measured using a gas exchange system 24 h after each application.

Spectroradiometry analyses revealed the significant effects of paint color (P ≤ 0.001) on

reflection, transmission, and absorption of PAR. Lighter colors including white, yellow,

orange, and red reflected 47-92% of PAR, while darker colors including green, black, and

dark blue absorbed 87- 95% of PAR. Accompanying gas exchange measurements revealed

that TCP was most negatively correlated with absorption of PAR (r = -0.959; P ≤ 0.001) and

that darker colors negatively impact TCP more than lighter colors. The results clearly

indicate that damage to turfgrasses with long-term painting will be difficult to avoid, and this

is particularly true with darker colors of paint.

58

Introduction

Painting of turfgrass athletic fields is a common practice throughout the world. It is

widely recognized that repeated paint applications degrade turfgrass quality. The underlying

basis for decline in quality, and thus the question of whether it can be avoided, has yet to be

resolved. It is conceivable that the negative impact of paint on turfgrass quality can be traced

to properties of the pigments used to produce each paint color. The wavelength range for

visible light overlaps with PAR, between 400 and 700 nm, and alterations in visible light to

produce specific colors could have negative effects on photosynthetically active radiance

(PAR), and the associated rate of turfgrass photosynthesis. This cause and effect relationship

was implied in a recent study where red and white paint were applied to perennial ryegrass

(Lolium perenne L.) (Reynolds et al., 2012). Applications of red paint absorbed 51% of PAR

and reduced total canopy photosynthesis (TCP) up to 75%, while applications of white paint

reflected 95% PAR and reduced TCP by only 20-45%.

Commonly used colors of athletic field paint influence light across the entire visible

spectrum. Paint colors are produced using varying pigment sources that selectively reflect,

transmit, and absorb specific wavelengths of light (Fig 1.). For example, red Fe2O3, a

commonly used pigment in red paint, produces a red color by reflecting approximately 20-

30% more visible light in the 600-700 nm range than in the remaining visible wavelengths

(Endrib, 1998). Because different colors would impact different spectral bands in the 400 to

700 nm range, it is likely that the degree of effects on TCP could differ greatly.

In addition to differences in pigments based on color, all pigments are designed to be

opaque such that the painted surface, in this case the turfgrass leaf, is hidden. As a result, not

59

only are various wavelengths of light altered in painted turfgrass canopies, but the total

amount of visible light hitting the leaf surface may be greatly reduced due to absorption by

paint pigments. Thus, there is the potential for painting to disrupt the light reactions of

photosynthesis and regulation of stomatal opening which may affect the supply of C for the

dark reactions (Taiz and Zeiger, 2010; Shimazaki et al., 2007).

In the experiments described in this manuscript, previous research (Reynolds et al.,

2012) is extended by evaluating changes in PAR and photosynthesis over a range of ten paint

colors. Lab experiments were performed to analyze how different paint colors altered

reflection, transmission, and absorption of PAR at specific broad- and narrow-band

wavelengths. Subsequent growth-chamber experiments evaluated the extent that the

alterations in PAR affected TCP of ‘Tifway’ hybrid bermudagrass [Cynodon dactylon (L.)

Pers. x C. transvaalensis Burtt-Davy]. The results provide a basis for understanding declines

in turfgrass quality associated with repeated applications of various colors of athletic field

paint.


Spectroradiometry

Ten colors of Pioneer Brite Stripe Airless Paint (Pioneer Athletics) were selected for

study. Pioneer Brite Stripe was chosen due to its widespread use on athletic fields as well as

its ability to be diluted at various ratios ranging from 1:1 to 4:1 v/v based on the product

label. It also allowed for uniform dilution across all colors, as opposed to pre-mixed

products that are not designed to be diluted. The ten colors selected were defined using the

60

Pantone Matching System (PMS) which is a standardized color reproduction system that

assigns specific reference numbers to each color (Hunt, 2011). Colors examined in this study

were selected to include the entire visible spectrum, and their respective PMS numbers are

presented in Table 1. Reflection, transmission, and absorption of PAR by each of these colors

was measured using a method established by Reynolds et al. (2012) that involves uniform

application of paint treatments to transparency film (3M PP2500, 3M) using a wet film

applicator (Gardco 8-Path, Gardco). This device allows a small quantity of liquid to be

applied to surfaces at a known wet thickness for subsequent testing. Each of the ten colors of

athletic field turf paint was diluted at a 1:1 ratio with water prior to application to the

transparency film. In order to achieve similar dried thicknesses for comparison, black, dark

blue, green, light blue, maroon, orange, purple, red, and yellow were each applied at a

uniform wet thickness of 0.625 mm while white was applied at a wet thickness of 0.375 mm.

This distinction was made due to the high amount of pigment solids present in white paint,

relative to other colors, and its characteristic ability to dry thicker. The final dried thickness

of each film was recorded using a digital micrometer to ensure uniformity among colors.

Reflection and transmission of PAR through each color (Fig. 1) was measured

between 400 and 700 nm at 0.5 nm intervals using an integrating sphere (LICOR 1800-12,

LI-COR) and spectroradiometer (Apogee Instruments). Measurements were performed on

three replications of each of the ten colors. The interior of the integrating sphere was newly

pressed barium sulfate and was used as the reflection reference as described in the

manufacturer’s instructions (LICOR 1800-12). The painted side of the transparency film

faced the inside of the integrating sphere for the reflection reference and sample readings.

61

For transmission sample and reference readings, the painted side of the transparency film

faced the outside of the integrating sphere. The light source used to illuminate the integrating

sphere was constant, but it’s location within the sphere varied between reference and sample

readings, as well as between reflection and transmission readings. Sample absorption was

calculated as sample absorption = 1 – reflection – transmission.

In addition to PAR, broad and narrowband spectral data were collected at specific

wavelengths to determine effects on light quality. Broadband wavelengths were defined as

400-500 nm and 600-700 nm, and narrowband wavelengths were defined as 410, 430, 640,

and 660 ± 10 nm. These bands are often grouped by color where blue light is considered to

be 400-500 nm and red light is considered to be 600 to 700 nm. Within these bands,

chlorophyll a is known to have peak spectral absorption at 410, 430, and 660 nm while peak

absorption for chlorophyll b occurs at 430 and 640 nm (Bell, 2000). Measurements of

reflection and transmission, and calculations of absorption at each of these wavelengths were

determined as previously described using the integrating sphere and spectroradiometer.


Growth chamber experiments were conducted at the Southeastern Plant Environment

Laboratory at North Carolina State University in Raleigh, NC. Sixty pots were prepared with

a 50:50 v/v sand and peat substrate based on the original “Cornell Mix” (Boodley and

Sheldrake, 1972). The substrate was steam-sterilized, placed into 15.8-cm diameter pots, and

planted with washed Tifway bermudagrass sod which was selected due to its widespread use

on athletic fields. After sodding, the pots were placed into a growth chamber maintained at

62

29/24oC (day/night) with a 12 h photoperiod (0700 h to 1900 h) and a photosynthetic photon

flux density of approximately 1000 µmol m-2

s-1

provided by a combination of incandescent

and fluorescent lamps. Water and nutrient solution were applied twice daily throughout the

bermudagrass establishment period and then once daily during experimental periods to

support adequate growth by preventing water or nutrient deficiencies. The ‘standard nutrient

solution’ is described in detail in the North Carolina State University Phytotron Procedural

Manual (NCSU, 2011). Pots were mowed one day prior to paint application and two days

after photosynthesis measurements at 2.5 cm using a handheld shear (194380 Oster

Showmaster, Oster).

Paint Application

Prior to application of paint treatments, turf in all sixty pots was allowed to reach

maturity, defined as uniform coverage, maximum density and quality, and then experimental

units were randomly divided into two sets for replication over time. Each replicate

experiment, referred to hereafter as Exp. 1 and 2, consisted of ten colors of athletic field turf

paint (Table 1) and three replications per color. Paint applications were made every seven

days for five consecutive weeks within each experiment, and Exp. 2 began after completion

of Exp. 1. Paint treatments were applied to pots using a CO2-pressurized sprayer with flatfan

nozzles (Teejet8004VS, Teejet Spraying Systems Co.) calibrated to apply approximately 168

L ha-1

. This rate was achieved by four applications in multiple directions to each pot, which

ensured uniform paint coverage on turfgrass leaves.

63

Photosynthesis Measurements

Carbon exchange rates were measured twenty-four hours after each of five weekly

paint applications and were determined by enclosing the turfgrass canopy in a transparent

plexiglass chamber (956 cm3) connected to a portable gas exchange system (LI-6400, LI-

COR Inc.). Measurements of carbon exchange rate were always taken between 1000 and

1500 h. Carbon exchange rates were measured in full light in the growth chamber and in

total darkness immediately after light measurements were recorded (achieved by covering the

plexiglass chamber with opaque black fabric). Measured carbon exchange rates under dark

conditions were considered to represent canopy, root, and soil respiration. Total canopy

photosynthesis (TCP) was calculated by adding the absolute value of dark respiration to the

observed carbon exchange rate in the light (Singh et al., 2011). Canopy temperature was

measured immediately prior to enclosure of the turfgrass in the transparent plexiglass

chamber using an infrared digital thermometer with an error range of ±3oC. (Fluke 63IR,

Fluke Inc.).


Data from spectroradiometry and growth chamber experiments were subjected to

ANOVA to determine treatment effects using PROC GLM (version 9.3, 2012; SAS Institute

Inc., Cary, NC). Total canopy photosynthesis and canopy temperature data produced

significant treatment effects, but TCP also showed interactions with experiment. Therefore,

TCP data from Experiments 1 and 2 were analyzed and presented separately with treatment x

experiment interactions reported in the appropriate ANOVA table. Canopy temperature data

64

showed no interaction with experiment and were therefore pooled for analysis. Treatments

within all experiments were subjected to Fischer’s Protected LSD test at the 0.05 probability

level when F-tests indicated significant treatment effects. Pearson’s correlation coefficients

were calculated to examine the relationship between TCP and reflection, transmission, and

absorption of light at various wavelengths using PROC CORR (version 9.3, 2012; SAS

Institute Inc., Cary, NC).

Results

Spectroradiometry Analyses

Reflection, transmission, and absorption of PAR and light in the broad and narrow-

band wavelengths were found to be different (P ≤ 0.001) for all colors (Table 2). Broadband

spectroradiometry indicated that white paint reflected the highest amount of PAR and black

paint reflected the least. Reflection of PAR varied strongly by color with white reflecting

92.6% followed by yellow (63.1%), light blue (51.6%), orange (47.0%), and red (41.2%)

reflecting the highest amounts. Reflection of PAR by the darker colors was much smaller and

included maroon (20.9%), green (11.9%), purple (10.7%), dark blue (6.8%), and black

(4.5%) reflecting the least. Inversely, absorption of total PAR was much higher by the darker

colors than the lighter colors, with black absorbing the most (95.4%) and white the least

(0.0%). Transmission of PAR also varied by color, but the magnitude of differences was

much smaller. Transmission ranged from 12.4% to 18.0% in the lighter colors white, yellow,

orange, and red, while in the darker colors maroon, green, purple, dark blue, and black,

transmission ranged from 0.1% to 4.7%.

65

A comparison of spectroradiometry data in the 400-500 nm and 600-700 nm

broadband wavelengths indicate the different impacts that pigments have within PAR. White

and black did not vary as much by broadband wavelength, as can be seen in Table 2 where

white reflected 91.8% of light between 400-500 nm and 94.1% between 600-700 nm and

black paint reflected < 5% of both, effects that aligned with those on overall PAR. However,

all other colors varied greatly by broadband wavelength. Yellow, for example, reflected

76.1% of light between 600-700 nm but only 13.2% between 400-500 nm. Orange reflected

almost ten times more light between 600-700 nm than 400-500 nm, while red reflected

almost nine times as much. Green paint reflected light within 400-500 nm and 600-700 nm

ranges at approximately equal amounts while light blue, dark blue, and purple were the only

colors to reflect more light between 400-500 nm than 600-700 nm.

The effects of color on transmission of light were also wavelength dependent for all

colors, yet the magnitude of differences between broadband wavelengths were much smaller

within each color. The effects on absorption of light were also wavelength dependent in all

colors except white and black and were inversely related to reflection, as expected. Although

narrowband data are not presented, they support the broadband wavelength data in that

differences in narrowband data based on color were similar to the reported differences in

broadband data with regard to reflection, transmission, and absorption at all measured

wavelengths.

66


Reductions in TCP as a result of all paint treatments were different (P ≤ 0.0001) in

Exp. 1 and 2 despite an interaction between treatment and experiment (P ≤ 0.0006; ANOVA

Table 3). Experiment (P = 0.6276) and replication (P = 0.8414) were not different, while

week and treatment by week interaction were both different (P ≤ 0.0001).

White paint proved to have the least impact on TCP of Tifway bermudagrass in both

experiments (Fig 2). Total canopy photosynthesis was maintained at 78% of the unpainted

control throughout five weeks in Exp. 1 and 83% in Exp. 2. Applications of yellow and

orange paint resulted in higher TCP rates than all other colors except white in both

experiments, ranging from 65-69% of the control in Exp. 1 and 71-75% in Exp. 2. Further

reductions in TCP based on severity included red paint, which had TCP rates of 50 and 53%

of the un-painted control in Exp. 1 and 2, light blue (48 and 47%), purple (36 and 33%),

maroon (41 and 32%), green (26 and 25%), black (15 and 18%), and dark blue (13 and 8%).

Canopy temperature was influenced by paint color and was different (P ≤ 0.001)

within and across Exp. 1 and 2. Canopy temperature data for both experiments were pooled

due to no effect of date, experiment, or treatment by experiment interaction. There were no

differences among white (31.4°C), yellow (32.3°C), orange (32.5°C) and untreated (32.3°C)

canopy temperatures. However, canopy temperatures did increase for red (33.4°C), light blue

(33.8°C), purple (35.9°C), green (36.9°C) and maroon (36.9°C), while the highest canopy

temperatures were produced by black (39.9°C) and dark blue (40.5°C) treatments. Standard

error values of canopy temperature measurements ranged from 0.3oC in orange to 0.7

oC in

green.

67

Pearson’s correlation coefficients in Table 4 and Fig. 3 define the relationship

between PAR and TCP over the range of paint colors. In Exp. 1, TCP was most highly

correlated with absorption of PAR (r = - 0.96; P ≤ 0.001), followed by positive correlations

with reflection (r = 0.93; P ≤ 0.001) and transmission of PAR (r = 0.84; P ≤ 0.001). In Exp 2,

the correlations were similar. The correlations between TCP and the reflection, transmission,

and absorption of light within the 600-700 nm wavelengths were approximately one and a

half to two times higher than within the 400-500 nm wavelengths in both experiments. For

example, in Exp. 1, Pearson’s correlation coefficient for TCP and reflection of 600-700 nm

wavelengths (r = 0.95; P ≤ 0.001) was more than twice as high as the correlation coefficient

for TCP and reflection of the 400-500 nm wavelengths (r = 0.45; P ≤ 0.05). Also in Exp. 1,

Pearson’s correlation coefficient for TCP and absorption of 600-700 nm wavelengths (r = -

0.93; P ≤ 0.001) was also more than twice as high as the coefficient for TCP and absorption

of 400-500 nm wavelengths (r = - 0.45; P ≤ 0.05). Pearson’s correlation coefficients for

narrowband wavelengths and TCP support the relationships between broadband wavelengths

and TCP (data not shown).

Canopy temperature increases as a result of paint color were most positively

correlated with absorption of PAR in Exp. 1 (r = 0.87; P ≤ 0.001) and Exp. 2 (r = 0.87; P ≤

0.001). Canopy temperature was negatively correlated with reflection and transmission of

PAR and broadband wavelengths. Correlation coefficients for canopy temperature and

reflection, transmission, and absorption were higher and more significant between 600-700

nm than between 400-500 nm in both experiments. Like TCP, data for correlations of canopy

temperature and narrowband wavelengths supported the broadband data.

68

Discussion

The hypothesis being tested in this research was that alterations in visible light by

paint pigments to produce a specific color would be coupled with alterations in PAR and

TCP within a painted turfgrass canopy. This hypothesis was based on the overlap of visible

light and PAR between 400 and 700 nm as well as the requirement that all paints be opaque

enough to adequately cover a leaf surface. Each of these has the potential to reduce total

PAR, as well as ‘filter’ wavelengths within PAR, reaching leaf surfaces.

The results of the spectroradiometry analyses and the measurement of TCP of Tifway

bermudagrass clearly support this hypothesis. A significant negative correlation was present

between absorption of PAR and Tifway bermudagrass TCP over the broad range of colors

examined. Darker colors absorbed a larger proportion of PAR, resulting in greater

suppression of TCP. Thus, it is reasonable to conclude that alterations in the amount of light

reaching the leaf surface and inhibited TCP are a major cause of suppressed growth and

subsequent declines in turfgrass health when painting occurs. Furthermore, it would be

expected that darker colors lead to greater damage to turfgrass health over extended periods.

This is supported by observations of the clipping collections throughout both experiments.

Darker colors had more suppressed growth than lighter colors, particularly in the later weeks

of both experiments. This likely results in less paint being removed through mowing as a

result of less vertical growth, more paint remaining in the turfgrass canopy, and thus more

shading. Attempts to collect and weigh clippings for analysis by color were unsuccessful due

to the inability to separate clippings from paint residue.

69

In addition to the effects of shading, another potential factor contributing to lower

TCP may have been increased plant and root respiration rates caused by increased canopy

temperatures. Leaf canopies painted with darker paint colors had higher canopy

temperatures, and it is generally understood that respiration increases with temperature until

40 to 50oC (Taiz and Zeiger, 2010).

Increases in respiration as a result of increased canopy temperatures based on paint

color could potentially contribute to the observed reductions in TCP given that TCP was

calculated by adding the absolute value of dark respiration to the observed carbon exchange

rate in the light. However, an analysis of dark respiration data used for TCP calculations

minimize that possibility as a confounding variable in painted turfgrass canopies. Dark

respiration data indicate that respiration actually decreases in canopies painted with darker

colors, despite any implications that respiration rates may increase as a result of increased

temperature. This likely reflects the dependence of respiration on concurrent photosynthesis

and its supply of carbohydrate.

Our results with paint are somewhat analogous with those from shading studies (e.g.

Bell et al., 2000; McBee, 1969; Ngouajio and Ernest, 2004; Trappe et al., 2011). More

specifically, Baldwin et al. (2009) found that shade fabrics filtering wavelengths from 360 to

720 nm reduced warm season grass clipping yields by as much as 79%. Decreases in Tifway

bermudagrass quality were wavelength-dependent, with yellow and red shade cloth less

damaging than cloth that was blue or black. For example, blue shade cloth that allowed only

passage of blue light for one and four weeks resulted in lower visual quality ratings than

yellow and red shade cloths that only allowed passage or yellow and red light. After eight

70

weeks of filtered light, blue and yellow shade cloths resulted in lower visual quality ratings

than red shade cloths. These results indicate the importance of red light on the health of

Tifway bermudagrass. Pearson’s correlation coefficients presented in Table 4 support this in

that TCP of Tifway bermudagrass was less affected by paint colors which absorbed a higher

percentage of blue light as opposed to red light. For example, darker colors including black,

dark blue, purple, and green absorbed the highest percentage of red light and also had the

greatest impacts on TCP, in addition to maroon. Inversely, lighter paint colors including

white, yellow, and orange that reflected the highest percentage of red light were the least

harmful to TCP.

Spectroradiometry data presented in Tables 2 and 4 indicate the ability of paint to

selectively absorb wavelengths within PAR and are important for several reasons. First, they

accurately represent the expected properties with regard to the pigments used to produce a

specific color, i.e., blue paints reflect more blue light than red light, red paints reflect more

red light than blue light, etc. Second, previous research has shown that various sources of

shade can selectively alter wavelengths within PAR, red/far-red ratios, etc. (Baldwin et al.,

2009; Bell et al., 2000). This supports the notion that various colors of paint can also create

various shading effects much like varying tree species, buildings, etc. create various shading

effects. Lastly, while blue light is important in many plant growth processes, red light is more

often associated with photosynthetic responses including the enhancement effect and the red

light response to stomatal opening (Taiz and Zeiger, 2010; Shimazaki et al., 2007).

In other types of studies with cotton (Gossypium hirsutum L.), higher reflection of

PAR had positive effects on plant growth when plastic surfaces painted white were placed

71

beneath canopies (Kasperbauer, 2000). Similarly with carrot (Daucus carota L.), lighter

colored plastic mulches had greater benefits than darker mulches (Antonious and

Kasperbauer, 2002). With athletic field tarps covering ‘Midnight’ Kentucky bluegrass (Poa

pratensis L.) at different times during the year, Minner et al. (2000) found that orange, white,

yellow, and red tarps consistently had the most positive effects on turf color after tarp

removal, while darker colored tarps were much more injurious. Goatley et al. (2007) showed

that various colored tarps altered PAR available for use on ultradwarf bermudagrass putting

greens where black, green, gray, white, and translucent tarps reduced PAR by 91-99%, 69-

79%, 36-49%, and 34%, respectively. It is worth mentioning that increased temperatures as a

result of all tarps, especially the darker colored tarps, have the potential to confound shading

effects in a manner that is different from painted turfgrass canopies given that paint and tarps

cover the turfgrass canopy by different means. However, the effects of different colored tarps

on turfgrass health are consistent with results from our paint experiments and illustrate the

dependence upon color.

Ultimately, the key for understanding color effects on PAR lies within the optical

properties of the pigments that produce different colors. Pigment sources for athletic field

paints include both organic and inorganic sources, each of which contribute various

properties with regard to color and application. Pigment classification in this paper will be

defined using the traditional properties associated with organic and inorganic pigments as

defined by Lambourne and Strivens (1999).

Inorganic pigments possess excellent hiding power, extreme fastness to light and

weathering, and excellent color stability (Endrib, 1998). They also produce various optical

72

effects through non-selective or selective reflection and absorption of light. The extreme

reflectiveness of white is produced by the non-selective scattering of visible light by the base

pigment TiO2, which is recognized as having the highest brightening power of all industrially

produced pigments (Stoye and Freitag, 1998). In contrast, the extremely high absorption (>

95%) of visible light/PAR by black is characteristic of the non-selective inorganic pigment C

black (Buxbaum and Pfaff, 2005). Carbon black is so effective at absorbing light that it

comprises approximately only 10% of the paint formulation (v/v) whereas other colors

contain as much as 31% pigment (v/v). Therefore, even at the lowest pigment concentration

of any color tested, black was still capable of absorbing the highest amount of visible light

based solely on the optical properties of black pigments.

Unlike with white and black, colors like red and yellow that are derived from

inorganic pigments selectively reflect and absorb light in a wavelength-dependent manner

(Herbst and Hunger, 2004). Yellow Fe2O3, for example, is known to reflect up to three times

more light in the longer wavelengths than in shorter wavelengths (Endrib, 1998), as was seen

in the spectroradiometry measurements (Table 2).

Regardless of reflective and absorptive properties, many inorganic pigments like

TiO2, C, and Fe2O3 are limited in the range of colors they can produce. Furthermore, most

inorganic pigments lack tinting strength and therefore produce dull shades when added to

white to produce various colors (Herbst and Hunger, 2004). Therefore, organic pigment

sources are often incorporated to produce colors that inorganic sources alone cannot (Table

1). For example, colors used in this study that contain both organic and inorganic pigment

73

sources include light blue (TiO2; phthalocyanine blue) and yellow (yellow Fe2O3; pyrazolone

orange).

Spectroradiometry analysis of each of the paint colors tested in this study accurately

represents the reflection and absorption characteristics one would expect based on the

pigment properties found in each color. Furthermore, low transmission (relative to reflection

and absorption) accurately represents the fact that all paints, regardless of color, must meet

the basic opacity requirement of blocking enough visible light to hide the turfgrass leaf.

The results presented in these experiments illustrate the color-dependent relationship

between available PAR and subsequent TCP within painted turfgrass canopies. This is a

direct result of the fact that visible light and PAR overlap between 400 and 700 nm and

therefore any alterations by paint pigments to produce a specific desired color are also very

likely to impact PAR and turfgrass growth. Reflection and transmission of PAR by lighter

colors of paint is likely still available for use within the turfgrass canopy in areas with

cracked leaf surfaces or partial paint coatings as well as on abaxial leaf surfaces and lower

portions of the canopy that may not have received paint. Furthermore, as painted turfgrasses

are mowed, reflection and transmission of PAR by lighter colors of paint can be useful for

photosynthesis in newly formed, unpainted leaves. However, the overwhelming ability of

pigments found in darker colors of paint to absorb PAR create such a profound shading effect

that it is unclear how damage to painted turfgrass can be avoided when using these colors.

Further research is needed on paint application techniques, rates, and product selection as

well as turfgrass management strategies that may reduce the amount of time leaves remain

painted, thus reducing duration under shade.

74

References

Antonious, G.F., and M.J. Kasperbauer. 2002. Color of light reflected to leaves modifies


Baldwin, C.M., H. Liu, L.B. McCarty, H. Luo, C.E.Wells, and J.E. Toler. 2009. Impacts of





Boodley, J.W. , and R. Sheldrake. 1972. Cornell peat-lite mixes for commercial plant

growing. Ext. Info. Bul. 43. Cornell Univ., Ithaca, NY.

Buxbaum, G., and G. Pfaff. 2005. Industrial inorganic pigments. WILEY-VCH Verlag

GmbH and Co. KGaA, Weinheim, Germany.


Germany.

Goatley, J.M., Jr., J.P. Sneed, V.L. Maddox, B.R. Stewart, D.W. Wells, and H.W. Philley.

2007. Turf covers for winter protection of bermudagrass golf greens. Online. Applied

Turf Science doi : 10.1094/ATS-2007-0423-01-RS.

Herbst, W., and K. Hunger. 2004. Industrial organic pigments. WILEY-VCH Verlag GmbH


Hunt, R.W., and M.R. Pointer. 2011. Measuring Colour. 4th

ed. John Wiley & Sons, Ltd.

Chichester, UK.

75



Lambourne, R., and T.A. Strivens. 1999. Paint and surface coatings. 2nd

ed. Woodhead

Publishing. Cambridge, England.



Minner, D.D., D. Li, V. Patterozzi, and J.J. Salmond. 2000. The effect of tarp color on

turfgrass growth. Iowa State Univ. Turfgrass Res. Rep. Available at

http://www.hort.iastate.edu/sites/default/files/imported/turfgrass/pubs/turfrpt/2000/tar

pstdyres2000.html (accessed 7 Jan. 2013).

North Carolina State University (NCSU). 2011. Phytotron Procedural Manual. NCSU

Technical Bulletin 244. North Carolina State University, Raleigh, NC.

http://www.ncsu.edu/phytotron/manual.pdf (accessed 7 Jan. 2013).

Ngouajio, M., and J. Ernest. 2004. Light transmission through colored polyethylene mulches

affects weed populations. Hort Sci. 39:1302-1304.

Reynolds, W.C., G.L. Miller, and T.W. Rufty. 2012. Athletic field paint impacts light

spectral quality and turfgrass photosynthesis. Crop Sci. 52:2375-2384.

SAS Institute. 2012. The SAS System for Windows. Release 9.3. SAS Inst., Cary, NC.

Shimazaki K., M. Doi, S.M. Assmann, and T. Kinoshita. 2007. Light regulation of stomatal

movements. Annu. Rev. of Plant Biol. 58:219-247.


76




Stoye, D., and W. Freitag. 1998. Paints, coatings, and solvents. WILEY-VCH Verlag GmbH



ed. Sinauer Assoc., Sunderland,MA.

Trappe, J.M., D.E. Karcher, M.D. Richardson, and A.J. Patton. 2011. Shade and traffic


77

Table 1. Pantone Matching System (PMS) numbers for ten colors of athletic field turf paint.

Color PMS number Pigment Pigment classification

Black Pantone Black C Carbon black Inorganic

Dark blue 287 Phthalocyanine blue Organic

Green 349 Phthalocyanine green Organic

Light blue 278 Titanium dioxide,

phthalocyanine blue Inorganic, Organic

Maroon 202 Quinacridone magenta Organic

Orange 158 Pyrazolone orange Organic

Purple 2735 Carbazole violet Organic

Red 186 Naphthol red Organic

Yellow 124 Yellow iron oxide,

pyrazolone orange Inorganic, Organic

White Not applicable†

Titanium dioxide Inorganic

† There is no PMS number for white paint.

78

Table 2. Reflection, transmission, and absorption of light in the 400-500 nm, 600-700 nm, and 400-700 nm wavelength ranges by ten colors of

athletic field paint.

Reflection Transmission Absorption

Treatment 400-700 400-500 600-700 400-700 400-500 600-700 400-700 400-500 600-700

%

White 92.6 a† 91.8 a 94.1a 12.4 c 9.1 a 13.9 c 0.0 j 0.0 i 0.0 i

Yellow 63.1 b 13.2 e 76.1 b 15.5 b 0.1 d 21.7 b 21.3 i 86.5 e 2.1 h

Light blue 51.6 c 76.2 b 45.8 d 0.6 f 2.5 c 0.3 f 47.6 f 21.2 h 53.7 e

Orange 47.0 d 6.6 h 65.7 c 18.0 a 0.1 d 28.5 a 34.9 h 93.1 b 5.7 g

Red 41.2 e 7.5 g 65.5 c 12.4 c 0.1 d 22.3 b 46.3 g 92.3 c 12.1 f

Maroon 20.9 f 9.1 f 30.3 e 4.7 d 0.2 d 8.4 d 74.2 e 90.5 d 61.2 d

Green 11.9 g 9.6 f 10.1 f 0.6 f 0.2 d 0.1 f 87.4 c 90.1 d 89.4 b

Purple 10.7 h 22.4 c 10.3 f 2.5 e 8.3 b 2.4 e 86.7 c 69.1 g 87.2 c

Dark blue 6.8 i 18.2 d 4.5 g 0.1 g 0.2 d 0.1 f 93.1 b 81.4 f 95.4 a

Black 4.5 j 4.7 i 4.4 g 0.1 g 0.1 d 0.1 f 95.4 a 95.1 a 95.4 a


Treatment *** *** *** *** *** *** *** *** ***

*** Significant at the 0.001 probability level.

†Means within columns followed by the same letter are not significantly different according to Fisher’s Protected LSD (P=0.05).

79

Table 3. Analysis of variance for normalized total canopy photosynthesis (TCP)

from weekly applications of ten colors of athletic field paint in a controlled

environment growth chamber during two 5-wk experiments at the Southeastern

Plant Environment Laboratory in Raleigh, NC.


Source df Mean

square F P > F

Experiment 1 0.1 0.2 0.6276

Treatment 9 1.7 277.8 <0.0001

Replication 2 0.1 0.2 0.8414

Week 4 0.1 17.2 <0.0001

Treatment x week 40 0.1 3.5 <0.0001

Treatment x experiment 9 0.1 3.4 0.0006

80

Table 4. Pearson’s correlation coefficients for reflection, transmission, and absorption of light through black, dark blue,

green, light blue, maroon, orange, purple, red, white, and yellow paint when correlated to total canopy photosynthesis

(TCP) and canopy temperature during two, 5-wk experiments.

Experiment 1

Experiment 2

PAR

Wavelength TCP

Canopy

temperature

TCP Canopy

temperature

Reflection 400-700 nm 0.93*** -0.84***

0.92*** -0.83***

400-500 nm 0.45* -0.43*

0.41* -0.41*

600-700-nm 0.95*** -0.84***

0.95*** -0.87***

Transmission 400-700 nm 0.84*** -0.75***

0.87*** -0.76***

400-500 nm 0.45* -0.30

0.30 -0.31

600-700-nm 0.76*** -0.68***

0.78*** -0.71***

Absorption 400-700 nm -0.96*** 0.87***

-0.96*** 0.87***

400-500 nm -0.45* 0.43*

-0.41* 0.41*

600-700-nm -0.93*** 0.85***

-0.94*** 0.87***

*Significant at 0.05 probability level.

**Significant at 0.01 probability level.

***Significant at 0.001 probability level.

81

Figure 1. Illustration of reflection, transmission, and absorption of light by athletic field

paint applied to a turfgrass leaf.

82

Figure 2.Normalized total canopy photosynthesis (TCP) rates of ‘Tifway’ bermudagrass 24

h after application of ten colors of athletic field paint during two 5-wk experiments in a

controlled environment growth chamber. Values for TCP were averaged over five weeks

and are reported as percent of un-painted control. Bars above each treatment represent

standard error.

83

Figure 3. Correlations of reflection, transmission, and absorption of PAR (400-700 nm)

with normalized total canopy photosynthesis (TCP) rates of ‘Tifway’ bermudagrass 24 h

after application of ten colors of athletic field paint during two 5-wk experiments in a

controlled environment growth chamber. Values for TCP were averaged over five weeks

and are reported as percent of un-painted control.

84

ATHLETIC FIELD PAINT COLOR IMPACTS TRANSPIRATION AND CANOPY

TEMPERATURE IN BERMUDAGRASS

William Casey Reynolds, Grady L. Miller,* David P. Livingston IIIb, and Thomas W. Rufty


7620, Raleigh NC 27695.

b.USDA-ARS, North Carolina State University, Campus Box 7620, Raleigh, NC 27695.




Formatted for submission to Crop Science


85

Abstract

Athletic field paints have varying impacts on turfgrass health which have been linked

to their ability to alter photosynthetically active radiation (PAR) and photosynthesis based on

color. It was further hypothesized they may also alter transpiration and canopy temperature

by disrupting gas exchange at the leaf surface. Growth chamber experiments evaluated the

effects of air temperature and six colors of paint on daily water loss and canopy temperature

in ‘Tifway’ bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy].

Daily water loss and canopy temperature were measured every 24 h using gravimetric

techniques and an infrared digital thermometer, while lab experiments examined the

thickness of white and black paint on the leaf surface. In un-painted bermudagrass canopies,

daily water loss increased (P ≤ 0.0001) with canopy temperature from 29 to 36oC while in

painted bermudagrass canopies, it decreased (P ≤ 0.0001) as canopy temperature increased

from 29 to 40oC. Yellow and white impacted transpiration and canopy temperature the least,

while black and blue caused the greatest reductions in transpiration and highest increases in

canopy temperature. Cross-sections of painted Tifway indicate paint may limit evaporative

cooling by clogging stomata. Increased absorption of radiant energy coupled with limited

evaporative cooling result in increased heat stress and decreased turfgrass performance in

painted canopies.

86

Introduction

Athletic field paints have increasingly become an integral part of sporting events

worldwide with an ever-increasing desire to produce bright, distinct, and often intricate logos

and designs. While these products are specifically designed and labeled for use on athletic

turf, repeated applications commonly result in declines in turfgrass quality, density, and

performance. The underlying basis for this decline has been linked to reductions in

photosynthetically active radiation (PAR) reaching the leaf surface due to absorption by paint

pigments, and is often color-dependent (Reynolds et al., 2012 and 2013). However, Reynolds

et al. (2013) also indicates that the interception of PAR by paint pigments is likely not the

only factor implicated in reductions of turfgrass quality in painted turfgrass canopies. For

example, in that study white paint absorbed 0.0% of PAR yet still produced total canopy

photosynthesis (TCP) rates in ‘Tifway’ hybrid bermudagrass [Cynodon dactylon (L.) Pers. x

C. transvaalensis Burtt-Davy] of only 78% and 83% of the un-painted control in two

separate experiments. Consequently, it is likely that other detrimental effects resulting from

athletic field paint applications are contributing to turfgrass decline, in addition to the effects

of shading.

One potential explanation for this may be that while photosynthesis is driven by PAR,

which would most certainly be affected by shading, transpiration relies upon adequate gas

exchange of carbon dioxide (CO2) and oxygen (O2) through leaf stomata. Given that paints

are designed to entirely coat leaf surfaces, it is reasonable to suspect that gas exchange may

be impeded by stomatal obstruction, potentially leading to carbon (C) starvation and reduced

evaporative cooling. Each of these could contribute to previously reported decreases in TCP

87

and increases in canopy temperature in painted turfgrass canopies (Reynolds et al. 2012 and

2013).

The impacts of various management practices and environmental factors on turfgrass

transpiration have been widely documented and include nitrogen rate, mowing height, shade,

herbicide application, and soil composition (Barton et al., 2009; Biron et al., 1981; Erickson

and Kenworthy, 2011; Feldhake et al., 1983; Wherley and Sinclair, 2009; Miller, 2000) as

well as species and variety (McGroary et al., 2011; Beard et al., 1992.). The impacts of

increasing temperature on turfgrass physiology and performance have also been documented

within and above optimal ranges (Du et al., 2010; Huang et al., 2009). While Reynolds et al.

(2012 and 2013) has documented increases in canopy temperature based on paint color,

research has yet to be conducted to explore the relationship between these temperature

increases and subsequent rates of transpiration.

The experiments described in this manuscript were initiated to investigate the impacts

of paint color on transpiration and canopy temperature in painted Tifway bermudagrass.

Growth chamber studies were conducted to establish the effects of paint color on Tifway

bermudagrass canopy temperature and subsequent rates of transpiration, while separate lab

experiments were conducted to determine the ability of paint to obstruct stomata. The results

presented in this research provide a further understanding of the effects of athletic field paint

color on turfgrass health and performance with specific focus on turfgrass transpiration and

canopy temperature.

88


Experimental Units and Paint Application

The research was conducted at the Southeastern Plant Environment Laboratory at

North Carolina State University in Raleigh, NC. Experimental pots were prepared with

Profile Greens Grade porous ceramic soil amendment (Profile Porous Ceramic Greens Grade,

Profile) and sodded with Tifway bermudagrass, which was selected due to its widespread use

on athletic fields. Each pot was 14-cm in diameter and 19-cm in depth and had a total volume

of 2,924 cm3. After sodding, the pots were placed into growth chambers maintained at

26/22oC (day/night) with a 12 h photoperiod (0700 h to 1900 h) and a photosynthetic photon

flux density of approximately 1000 µmol m-2

s-1

provided by a combination of incandescent

and fluorescent lamps. Water and nutrient solution were applied twice daily throughout the

bermudagrass establishment period and then once daily during experimental periods. The

‘standard nutrient solution’ is described in detail in the North Carolina State University

Phytotron Procedural Manual (NCSU, 2011). Pots were mowed twice weekly at 2.5 cm using

a handheld shear (194380 Oster Showmaster, Oster).

Prior to the initiation of Study 1 and 2, turf in all pots was allowed to reach maturity

and then experimental units were randomly divided into two sets per study for replication

over time. Each replicate experiment within Study 1, hereafter referred to as Exp. 1 and 2,

consisted of three replications of un-painted Tifway. Replicate experiments within Study 2,

hereafter referred to as Exp. 3 and 4, consisted of an un-painted control and six colors of

Pioneer Brite Stripe athletic field paint (Pioneer Athletics) with three replications per

treatment. Colors were defined using the Pantone Matching System (PMS) which is a

89

standardized color reproduction system that assigns specific reference numbers to each color

(Hunt, 2011). Colors examined in this study and their respective PMS numbers are presented

in Table 1. Paint applications were made every seven days for five consecutive weeks within

Exp. 1 and 2 using a Pioneer Brite Striper 3000 high pressure field marking machine (Pioneer

Athletics) with an Airless nozzle (Airlessco 219ST, Airlessco) calibrated to apply 9,903 L ha-

1. This rate was selected after calibration experiments with professional and university field

managers in order to apply a pressure and rate similar to that often used in highly managed

athletic turf.

Apparent Transpiration

Study 1

Apparent transpiration as a result of air temperature was determined gravimetrically

by the mass balance method. All pots were placed into a growth chamber at 26/22 oC,

saturated and allowed to drain to field capacity for 24 h prior to measurements of daily water

loss. Sod, roots, and substrate for all pots were then transferred to pots without drainage holes

to prevent further water loss due to drainage. The dense root structure and fine texture of the

porous ceramic substrate allowed for transferal of pots after the 24 h drainage period to pots

without drainage holes with no loss of substrate, roots, or water. Daily water loss was

determined by weighing the pots every 24 h for six days, and the amount of water lost each

day was returned to the pot after weighing. This allowed each pot to remain at the original

weight recorded on day one such that the pots did not encounter drought stress at any point

during the experiments. Apparent transpiration was calculated in mm day-1. At the end of

90

each week, all pots were transferred back to drainage pots before being re-saturated, allowed

to drain to field capacity for 24 h, and re-potted back into solid pots. Solid pots were placed

back into the growth chamber and the daytime temperature was raised by 3 o

C. Daily water

loss measurements were collected in the same manner as week one, and this continued as

daytime temperatures were raised by 3oC per week for five weeks. The day/night

temperatures for weeks 1 through 5 were 26/22 oC, 29/22

oC, 32/22

oC, 35/22

oC, and 38/22

oC,

respectively. These values were chosen based on the chamber’s ability to reach 38oC as its

maximum limit. Canopy temperature was measured immediately prior to weighing using an

infrared digital thermometer (Fluke 63IR, Fluke Inc.), while air temperature and relative

humidity were recorded every 24 h using a temp/RH data logger (HOBO pro V2, Onset

Computer Corp.)

Study 2

Apparent transpiration as a result of paint color was determined gravimetrically in the

same manner as Study 1. However, in Study 2, the chamber temperature was maintained at

26/22oC throughout the entire five weeks of Exp. 3 and 4, while paint treatments were

applied weekly for each of the five weeks within both experiments. All pots were saturated

and allowed to drain to field capacity for 24 h prior to application of paint treatments. At the

end of each week, all pots were transferred back to drainage pots before being re-saturated,

allowed to drain to field capacity for 24 h, re-potted back into solid pots, and then re-painted

before being placed back into the growth chamber. Canopy temperature, air temperature, and

relative humidity were each recorded in the same manner as Study 1.

91

Paint Thickness

The thickness at which paint dries on the turfgrass leaf was determined by randomly

selecting three leaves one day after application of white and black paint. White and black

were selected to provide a range of potential dried thicknesses due to white containing the

most pigment on a v:v basis of pigment to solution and black containing the least. Each of the

three leaves selected in both colors was visually inspected for uniform paint coverage and

then cut to a length of 1-cm measured from the leaf tip towards the leaf sheath. Leaves were

blocked in hot paraffin with the leaf-tip down and allowed to cool prior to sectioning. A

microtome (Leica RM2255, Leica Biosystems) with an Extremus Low Profile Disposable

Blade (C.L. Sturkey, Inc.) set at an angle of zero degrees was used to section each leaf.

Leaves were sectioned by location on the leaf and included tip, center, and base where each

was 2.5mm, 5.0mm, and 7.5mm from the leaf tip, respectively. Ten sections within each leaf

location were cut at a thickness of 20µm each, floated on water, and placed onto glass

microscope slides. Images were taken of each 20µm section using a digital camera (Sony

DSC707) attached to a 50i microscope (Nikon Eclipse) with a 10X objective and 30W

halogen lamp. Thickness of each color was measured using a 10X scale in µm increments at

five randomly selected places on each 20µm section. Each of the five paint thickness

measurements per leaf section was analyzed as a sub-sample within the ten sections per

location per leaf.

92


Data from growth chamber and paint thickness measurements were subjected to

ANOVA to determine treatment effects (PROC GLM, SAS Institute Inc., Cary, NC).

Apparent transpiration data in the un-painted experiments produced significant effects based

on day/night temperature treatments as well as an interaction with temperature. Painted

experiments produced significant color effects as well as a color by experiment interaction.

All apparent transpiration data were analyzed and presented separately by experiment due to

interactions with temperature (Exp. 1 and 2) and color (Exp. 3 and 4). Canopy temperature

data in the painted experiments were not different by experiment, but did produce color

interactions with experiment and were therefore also separated by experiment for further

analysis. Treatments within all experiments were subjected to Fischer’s Protected LSD test at

the 0.05 probability level when F-tests indicated significant treatment effects.

Discriminant analysis was also performed to further determine the impact of color on

canopy temperature and water loss. Discriminant analysis was performed in SAS using

PROC DISCRIM (version 9.3, 2012; SAS Institute Inc., Cary, NC) to determine whether

information about canopy temperature (oC) and daily water loss (mm day

-1) expressed

through a quadratic discriminant rule is useful in characterizing the color that grass was

painted, or equivalently, the group that the observation belongs to.

Results

Transpiration in un-painted bermudagrass canopies increased between 26 and 38oC in

Exps. 1 and 2 (Table 2) and were dependent upon daytime air temperature in the growth

93

chamber (Table 3). In Exp. 1, daily water loss increased from 8.4 mm day-1

at 26/22oC to

10.5 mm day-1

at 38/22oC, while in Exp. 2 it increased from 10.5 mm day

-1 to 15.2 mm day

-1

over the same range of temperatures. Furthermore, daily water loss in Exp. 1 was higher each

week that daytime air temperature increased, while in Exp. 2 it increased each week except

for weeks two and three, despite a 3oC increase in daytime air temperature from 29/22 to

32/22oC.

Canopy temperature increased with air temperature throughout all five weeks of

Exps. 1 and 2 and was slightly above the respective air temperatures of 26/22, 29/22, and

32/22oC, but slightly below the respective air temperatures of 35/22 and 38/22

oC. For

example, during weeks one through three in Exp. 1 the daytime air temperature in the growth

chamber was 26, 29, and 32oC, respectively, while the average daily canopy temperature was

29.3, 31.8, and 33.7oC. However, average daily canopy temperature during weeks four and

five were 34.6oC and 36.2

oC, and even though they increased from weeks one through three,

they were below their respective daytime air temperatures of 35 and 38oC. The relationship

between canopy temperature and air temperature in Exp. 2 was similar.

Transpiration in painted bermudagrass canopies was affected by color, as indicated in

Table 5. In Exp. 3, average daily water loss in the un-painted control was 9.1 mm day-1

and

was less affected by yellow (8.3 mm day-1

) and white (8.2mm day-1

) than red (7.8 mm day-1

)

and orange (7.8 mm day-1

). Applications of black (7.0 mm day-1

) and blue (5.1 mm day-1

)

had the most negative impacts. In Exp. 4, the range of effects based on color was similar, but

the absolute values for transpiration were higher for all colors. For example, average daily

water loss in the un-painted control was 2.6 mm day-1

higher than the control in Exp. 3, while

94

yellow, white, red, and orange were between 2.2 and 2.5 mm day-1

higher, and black and blue

were 1.8 and 1.6 mm day-1

higher than in Exp. 3. In Exps. 3 and 4, yellow impacted

transpiration the least and blue impacted transpiration the most. Percent reductions relative to

the control ranged from 8.8% by yellow to 43.9% by blue in Exp. 3 and 8.5% by yellow to

42.7% by blue in Exp. 4.

Analysis of transpiration by week (Fig. 1) reveals that in addition to reductions

throughout all weeks of Exp. 3 and 4 there were differences within weeks as well. The effects

of blue on daily water loss were more harmful over all weeks, and were also more

immediate. By week two of Exp. 3 and 4, blue resulted in the lowest daily water loss of all

colors and remained the lowest throughout all five weeks of both experiments. By week three

in both experiments, black resulted in the lowest daily water loss of all colors except blue.

Orange, red, and yellow resulted in daily water loss similar to the un-painted control early in

both experiments, but were each lower by week three in Exp. 1 and week two in Exp. 2.

White also resulted in daily water loss less than the un-painted control in both experiments

except during week five of Exp. 1 and week four of Exp. 2 where they were no different.

Paint color also impacted canopy temperature in painted bermudagrass canopies,

where it increased from the un-painted control in all colors except white (Table 5). In Exp. 1,

black (40.5oC) caused the largest increase in canopy temperature from the un-painted control

(28.9oC) followed by blue (39.6

oC), red (33.2

oC), yellow (30.7

oC), and orange (30.0

oC). In

Exp. 2 black (40.2oC) and blue (39.6

oC) caused the largest increase from the un-painted

control (29.4oC) followed by red (32.5

oC), orange (30.7

oC), and yellow (30.5

oC). White,

95

however, resulted in a lower canopy temperature (28.3oC), relative to the control in Exp. 1,

and a canopy temperature (29.3oC), no different than the control in Exp. 2.

The relationship between transpiration and canopy temperature in painted

bermudagrass canopies is revealed by Fig. 2 as well as Table 6. Average daily water loss in

painted turfgrass canopies decreased as canopy temperature increased and was dependent

upon color (Fig. 2). Black and blue resulted in higher canopy temperature and less water

loss, while orange, yellow, and white resulted in canopy temperatures and water loss more

similar to the un-painted control (Fig. 2). Red paint appeared to increase canopy temperature

and decrease water loss relative to the un-painted control, but its effects were not as great as

black and blue.

The cross-validation summary using quadratic discriminant analysis (Table 6)

supports Fig. 2 in that transpiration and canopy temperature resulting from applications of

orange, yellow, and white were more similar to the un-painted control than applications of

red, black, and blue. Results from Table 6 also indicate the ability to distinguish between

light and dark colors, but not within light and dark colors. For example, quadratic

discriminant analysis of transpiration and canopy temperature reveals that the un-painted

control was wrongly classified as yellow 10.0% of the time, orange 12.7% of the time, and

white 30.5% of the time. Furthermore, similarities between the un-painted control and light

colors of paint result in error count estimates of 53.8%, which illustrate the inability to

distinguish between the un-painted control and light colors. Yellow had the highest error

count estimates (78.3%) due to it being mistaken for the un-painted control, orange, red, and

white between 11.1 and 31.1% of the time.

96

Despite the inability of quadratic discriminant analysis to distinguish between the un-

painted control, white, yellow, and orange, it never misclassified them as black or blue.

Inversely, black and blue were never mis-classified as the un-painted control, orange, white,

or yellow which resulted in the lowest error count estimates (28.8 to 39.4%) of any color.

However, black and blue were wrongly classified for each other between 18.3 and 28.3% of

the time. Red was the only color that was wrongly classified as black or blue, occurring 9.3%

of the time.

Analysis of paint thickness revealed that the dried thickness of paint on the leaf is

dependent upon color (P ≤ 0.001) and not leaf location (P ≤ 0.317), yet there was a color by

leaf location interaction (P ≤ 0.002). White paint dried thicker than black at the tip, center,

and base of each leaf as well as the average of all locations. The thickness of white paint

measured at the tip, center, and base of turfgrass leaves was 43.3, 46.7, and 42.1 µm,

respectively. For black paint, measured thickness for each of these three locations was 21.8,

21.9, and 26.9µm, respectively.

Discussion

Increases in transpiration with increasing air temperature (26 to 38oC) in Study 1

indicate the ability of un-painted bermudagrass to maintain stomatal apertures sufficient to

actively transpire within, and slightly above, previously reported temperature optimum of 27-

35oC (Dipaola and Beard, 1992). This is consistent with previous research in other warm-

season turfgrass species where transpiration rates increase with air temperature. Green et al.

(1991a) reported average daily water loss in zoysiagrass (Zoysia spp.) to be between 6.1 and

97

8.5 mm day-1

when daily maximum air temperatures ranged from 24.6 to 31.6oC,

respectively. Green et al. (1991b) reported similar results in St. Augustinegrass

[Stenotaphrum secundatum (Walt.) Kuntz] where water loss ranged from 7.6 to 9.7 mm day-

1, with daily maximum air temperatures ranging from 32.8 to 36.6

oC, respectively. Increased

transpiration in Exp. 2 relative to Exp. 1 is likely a result of lower relative humidity in the

growth chamber during Exp. 2. The relative humidity in the growth chamber during Exp. 2

was 27.7% while in Exp. 1 it was 44.6%, which resulted in higher water loss at all days and

weeks in Exp. 2 than in Exp. 1.

Throughout the entire five weeks of both Exp. 1 and 2, canopy temperatures in the

un-painted bermudagrass pots fluctuated ±6.9oC in Exp. 1 and ±7.0

oC in Exp. 2. This is

approximately 58% of the range of air temperatures (26-38oC) the pots were exposed to

throughout the study. Furthermore, canopy temperature was within 1.1% to 12.6% of the air

temperature in the growth chamber at any single point during the study. As such, data from

Study 1 illustrate the ability of transpiration to moderate canopy temperature in un-painted

bermudagrass canopies throughout the optimum range of 27-35oC, and even up to 38

oC,

which is the maximum temperature of the growth chambers used in this study. This is

particularly true at higher air temperatures during weeks four and five where transpiration

was able to maintain canopy temperature below the air temperature in the growth chamber.

However, results from Study 2 demonstrate that the relationship between

transpiration and canopy temperature changes dramatically in painted bermudagrass

canopies. This is supported by Fig. 2 in that as canopy temperature increases in painted

bermudagrass canopies, daily water loss decreases, an effect contrary to that which was

98

established in Study 1. A potential explanation for this lies in the fact that athletic field paint

has other impacts on painted turfgrass canopies that likely supersede the relationship between

transpiration and canopy temperature. These include reductions in total canopy

photosynthesis (TCP), stomatal obstruction by paint pigments, and heat stress due to

increased light absorption.

Reynolds et al. (2012 and 13) established the color-dependent effects of athletic field

paint on bermudagrass TCP, and they are similar to the effects established in this study where

lighter colors were less damaging than darker colors. Reductions in TCP were linked to

absorption of photosynthetically active radiation (PAR) in which darker colors of paint

absorbed more PAR than lighter colors. For example, white, yellow, and orange, which

absorbed between 0.0 and 34.9% PAR, were less harmful to TCP than red, which absorbed

46% PAR. Colors most harmful to TCP were blue and black, which absorbed 93.1 and

95.4% of PAR and reduced TCP by 83.5 and 89.5%, respectively.

Stomata are regulated in a temporal manner in which they open during the day and

remain closed at night, closely following photosynthesis. Shading effects produced by darker

colors of paint capable of reducing photosynthesis could also be responsible for decreases in

transpiration due to the stomatal dependence on photosynthesis and light to regulate their

opening. The dependence of stomatal opening on light, particularly blue (400-500 nm) and

red (600-700 nm) light, is commonly referred to as the red light response and blue light

response. While blue light stomatal opening is primarily a signaling response, red light

stomatal opening is primarily driven by photosynthesis. These are spatially separated in the

leaf where the blue light response occurs primarily in guard cells present on either side of

99

stomata, while the red light response occurs in guard cells and mesophyll cells (Shimazaki et

al., 2007). Both of these cell types, and the light responses within them, are likely impacted

by applications of athletic field paint that cover the turfgrass leaf, preventing adequate light

interception (Fig. 3).

Furthermore, in addition to overall reductions in light interception, these reactions

could also be affected in a color-dependent manner. The effects of various colors of athletic

field paint on light interception at various wavelengths have previously been established.

White paint has been shown to reflect > 90% of visible light/PAR across all wavelengths, but

reflection of light by other other colors like orange, red, and yellow is more wavelength-

dependent (Reynolds et al., 2013). For example, orange, red, and yellow reflect between 65.5

and 76.1% of light between 600-700 nm but absorb between 86.5 and 93.1% of light between

400-500 nm. Light that is reflected by paint pigments is still available for use in painted

turfgrass canopies in areas with cracked leaf surfaces or partial paint coatings as well as on

abaxial leaf surfaces and lower portions of the canopy that may not have received paint.

Furthermore, as painted turfgrasses are mowed, reflection and transmission of PAR by lighter

colors of paint can be useful for photosynthesis in newly formed, unpainted leaves. However,

black and blue absorb > 93.1% of light across all wavelengths. Unlike light that is reflected

or transmitted by paint pigments, light that is bound within paint pigments is unavailable for

use by photosynthesis. As a result, it is reasonable to expect that applications of athletic field

paint have the potential to reduce transpiration in a color-dependent manner by limiting

signaling responses to blue light as well as limiting photosynthetic responses to red light.

Furthermore, expected limitations on photosynthesis and transpiration would be greater in

100

darker colors of paint, due to their innate ability to absorb large proportions of PAR, as well

as wavelengths within PAR.

In addition to limiting photosynthesis, which may impact transpiration, light

interception by paint pigments also has the potential to impact transpiration through heat

stress. Average daily canopy temperatures for white, yellow, orange, and red ranged

between 28.3 and 33.2oC in Study 2, which are well within the ideal temperature range of

bermudagrass (27-35oC). However, blue and black paint, which impacted transpiration the

most (Table 5; Figs. 1 and 2) raised canopy temperature well above the ideal range of 27-

35oC to between 39.6 and 40.5

oC. Increased light absorption by paint pigments, particularly

those found in black and blue, result in the necessity to dissipate this excess energy as heat.

The effects of heat stress on bermudagrass physiology and metabolism have

previously been investigated. Du et al. (2010) and Shen et al. (2009) defined heat stress as

day/night temperatures of 45/40oC and 44/40

oC, respectively. In other species with C4

metabolism, heat stress has been defined as 30-42oC and has been linked to direct inhibitions

of the Rubisco (ribulose 1,5-bisphosphate carboxylase-oxygenase) enzyme (Crafts-Brander

and Salvucci, 2000; Salvucci and Crafts-Brander, 2004). Specific research to investigate the

direct impacts of heat stress in painted turfgrass canopies has yet to be performed. However,

results from Study 2 indicate that black and blue paint have the potential to raise canopy

temperatures to within previously reported heat stress ranges, particularly in subtropical or

tropical climates where temperatures reach or exceed the optimum growing range for warm-

season turfgrasses.

101

In addition to increased absorption of radiant energy, the relationship between

reduced transpiration and increased heat stress in painted turfgrass canopies is also likely

linked to the ability of paint pigments to obstruct gas exchange at the leaf surface, as

indicated by the images in Fig. 3. Pigments present in athletic field paint, regardless of color,

are held in place on the leaf by a resin, which is the component of the formulation designed

to adhere to leaf surfaces (Reynolds, 2012 and 2013). Images from Fig. 3 illustrate that paint

noticeably coats the leaf surface with solid pigment particles being held in place by the resin.

As such, the ability of CO2 to enter the stomata, as well as O2 to exit the stomata is likely

impeded. Therefore, any reductions in gas exchange at the leaf surface would almost

certainly reduce the ability of transpiration to moderate canopy temperature in painted

turfgrass canopies, thus contributing to heat stress. Furthermore, the inherent properties of

pigments found in dark colors of paint to absorb a larger proportion of incident light would

certainly lead to greater potential for heat stress.

The importance of transpiration in moderating temperature fluctuations in plants is

due to the fact that as water evaporates through leaf stomata into the atmosphere, the latent

heat of vaporization of water moderates the temperature of transpiring leaves that would

otherwise increase due to absorption of solar radiation (Taiz and Zeiger, 2010) As such, in

painted turfgrass canopies there is likely a collective effect where increased absorption of

light energy, particularly by darker colors, results in temperature increases that the plant

cannot moderate through transpiration, due to stomatal obstruction and/or closure by

photosynthetic or light responses.

102

It is worth mentioning that in Fig. 3, white paint was applied at a 1:1 dilution with

water in the same manner as in Study 2. However, application of 1:1 dilutions of black paint

resulted in a paint film that was too thin to uniformly coat the leaf, thus preventing adequate

coverage and measurements of thickness. In order to obtain uniform coverage using black

paint, it was applied without being diluted yet still produced a thinner coating than white

paint at a 1:1 dilution. This is due to the lower percentage of pigment solids present in black

paint, relative to white paint, and is consistent with previous research where black paint has

been reported to contain approximately 20% less pigment than all other colors of paint

(Reynolds et al., 2013). Therefore, even at the lowest pigment concentration of the six colors

tested, black is able to raise canopy temperature and reduce transpiration more than any color

except blue.

The relationship between canopy temperature, reduced transpiration, and heat stress

in painted turfgrass canopies is likely all inter-connected. Previously reported photosynthetic

reductions, combined with decreased transpiration and heat stress all contribute to commonly

observed declines in turfgrass health and performance as a result of athletic field paint

applications. These effects are more damaging in darker colors of paint including black and

blue due to increased absorption of light that cannot as readily be dissipated as heat, likely

due to stomatal obstruction and reductions in transpiration. These effects are an un-avoidable

consequence of the innate properties of paint pigments as well as the necessity to apply

sufficient amounts of paint to produce bright, uniform lines and logos on athletic turf.

103

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evapotranspiration and growth of a warm-season turfgrass. Agron. J. 101:17-24.

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moisture. Agron. J. 73:85-90.

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Monograph 32. Agronomy Society of America, Madison, WI.

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(C3) to heat stress. Physiologia Plantarum. 141:251-264.

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stress in warm-season and cool-season turfgrasses. HortScience 44(7):2009-2014.

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alters light spectral quality and bermudagrass photosynthesis. (in press)


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106

Table 1. Pantone Matching System (PMS) numbers for six colors of athletic

field turf paint.

Color PMS number Pigment

Black Pantone Black C Carbon black

Blue 287 Phthalocyanine blue

Orange 158 Pyrazolone orange

Red 186 Naphthol red

Yellow 124 Yellow iron oxide, pyrazolone orange

White Not applicable†

Titanium dioxide

† There is no PMS number for white paint.

107

Table 2. Un-painted ‘Tifway’ bermudagrass daily water loss (mm day-1

) , canopy temperature, and

relative humidity as a result of six day/night air temperature treatments (26/22, 29/22, 32/22, 35/22,

and 38/22oC) in a controlled environment growth chamber during two 5-wk experiments at the

Southeastern Plant Environment Laboratory in Raleigh, NC.


Temperature

Daily

water loss

Average daily

canopy temperature†

Daily

water loss

Average daily

canopy temperature

mm day -1

oC mm day

-1

oC

26/22oC 8.4 e 29.3 e 10.5 d 29.1 e

29/22oC 8.9 d 31.8 d 12.1 c 31.6 d

32/22oC 9.3 c 33.7 c 12.5 c 33.2 c

35/22oC 10.2 b 34.6 b 14.3 b 34.2 b

38/22oC 10.5 a 36.2 a 15.2 a 36.1 a


*** *** *** ***

***Significant at the 0.001 probability level †Daily canopy temperature recorded every 24 h immediately prior to daily loss measurements.

108

Table 3. Analysis of variance for un-painted ‘Tifway’ bermudagrass daily water loss

(mm day-1

) as a result of six day/night air temperature treatments (26/22, 29/22, 32/22,

35/22, and 38/22oC) in a controlled environment growth chamber during two 5-wk

experiments at the Southeastern Plant Environment Laboratory in Raleigh, NC.


Source df

Mean

square F P > F

Experiment 1 521.2 1269.3 <0.0001

Week 4 65.6 159.7 <0.0001

Day(week) 25 5.7 13.9 <0.0001

Experiment x week 4 8.4 20.4 <0.0001

Experiment x day(week) 29 2.0 2.5 0.0006

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Table 4. Analysis of variance for ‘Tifway’ bermudagrass daily water loss (mm day-1

) due to

weekly applications of six colors of athletic field paint in a controlled environment growth

chamber during two 5-wk experiments at the Southeastern Plant Environment Laboratory in

Raleigh, NC.


Source df

Mean

square F P > F

Experiment 1 1481.6 2059.9 <0.0001

Color 6 378.4 526.1 <0.0001

Experiment x color 6 5.6 7.8 <0.0001

Week 4 123.3 171.5 <0.0001

Day(week) 25 33.9 47.1 <0.0001

Week x experiment 4 3.7 5.2 0.0004

Experiment x day(week) 25 0.6 0.8 0.7050

Week x color 24 23.1 32.1 <0.0001

Color x day(week) 150 1.2 1.6 <0.0001

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Table 5. ‘Tifway’ bermudagrass daily water loss and temperature response from weekly

applications of six colors of athletic field paint during two 5-wk experiments at the Southeastern

Plant Environment Laboratory in Raleigh, NC.


Treatment

Daily

water loss

Average daily

canopy temperature†

Daily

water loss

Average daily

canopy temperature

mm day -1

oC mm day

-1

oC

Control 9.1 a 28.9 f 11.7 a 29.4 d

Yellow 8.3 b 30.7 d 10.7 b 30.5 c

White 8.2 b 28.3 g 10.5 bc 29.3 d

Red 7.8 c 33.2 c 10.3 cd 32.5 b

Orange 7.8 c 30.0 e 10.0 d 30.7 c

Black 7.0 d 40.5 a 8.8 e 40.2 a

Blue 5.1 e 39.6 b 6.7 f 39.6 a


Treatment *** *** *** ***


†Daily canopy temperature recorded every 24 h immediately prior to daily loss measurements.

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Table 6. Quadratic discriminant analysis of canopy temperature (oC) and daily water loss (mm day

-1) in Tifway

bermudagrass as a result of weekly applications of six colors of athletic field paint and an un-painted control

during two 5-wk experiments at the Southeastern Plant Environment Laboratory in Raleigh, NC.

Actual

Predicted

Black

Blue

Control

Orange

Red

White

Yellow

Black 109 (60.5)†

51 (28.3) 0 (0.0) 0 (0.0) 20 (11.1) 0 (0.0) 0 (0.0)

Blue 33 (18.3) 128 (71.1) 0 (0.0) 0 (0.0) 19 (10.5) 0 (0.0) 0 (0.0)

Control 0 (0.0) 0 (0.0) 83 (46.1) 23 (12.7) 1 (0.5) 55 (30.5) 18 (10.0)

Orange 0 (0.0) 0 (0.0) 25 (13.8) 64 (35.5) 19 (10.5) 33 (18.3) 39 (21.6)

Red 1 (0.5) 16 (8.8) 15 (8.3) 23 (12.7) 101 (56.1) 3 (1.6) 21 (11.6)

White 0 (0.0) 0 (0.0) 52 (28.8) 40 (22.2) 0 (0.0) 77 (42.7) 11 (6.1)

Yellow 0 (0.0) 0 (0.0) 34 (18.8) 56 (31.1) 31 (17.2) 20 (11.1) 39 (21.6)

Error count estimates for color

Rate 0.3944 0.2889 0.5389 0.6444 0.4389 0.5722 0.7833

† Values preceding parentheses represent the number of times a color was classified as another color while

values within parentheses represent the percent of the total.

112

Experiment 3

1 2 3 4 5

Wa

ter

Lo

ss (

mm

da

y -1

)

2

4

6

8

10

Black

Blue

Control

Orange

Red

White

Yellow

Experiment 4

Week

1 2 3 4 52

4

6

8

10

12

Black

Blue

Control

Orange

Red

White

Yellow

Figure 1. Average daily water loss (mm day-1

) of ‘Tifway’ bermudagrass measured every

24 h for six days per week during two 5-wk experiments in a controlled environment

growth chamber at the Southeastern Plant Environment Laboratory in Raleigh, NC.

Values represent daily average water loss, and bars for each treatment represent

standard error.

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Experiment 3

25 30 35 40 45 50 55

Lo

ss (

mm

da

y -1

)

2

4

6

8

10

12

14

16

Black

Blue

Orange

Red

White

Yellow

Control

Experiment 4

Canopy Temperature (oC)

25 30 35 40 45 50 552

4

6

8

10

12

14

16

18

Black

Blue

Orange

Red

White

Yellow

Control

Figure 2. Daily water loss (mm day-1

) and canopy temperature (oC) of ‘Tifway’

bermudagrass measured every 24 h for six days per week during two 5-wk experiments in a

controlled environment growth chamber at the Southeastern Plant Environment Laboratory

in Raleigh, NC.

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A. White 1:1 dilution

B. Black no dilution

Figure 4. Digital images of 20µm cross-sections of ‘Tifway’ bermudagrass embedded in

paraffin after one application of white (A.) and black (B.) athletic field paint. White paint

has been diluted with water at v:v ratio of 1:1 and black paint was not diluted. Images were

taken at 10x magnification and cropped to an image size of 856 x 560 pixels.

ABSTRACT REYNOLDS, WILLIAM CASEY. The Impacts of Athletic Field Paint on Light Spectral

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